diff --git a/DESCRIPTION b/DESCRIPTION
index ab9d683..552bb03 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -28,3 +28,4 @@ Suggests:
 VignetteBuilder: knitr
 LazyLoad: yes
 LazyData: yes
+RoxygenNote: 7.3.1
diff --git a/R/utility.R b/R/utility.R
index 1218644..c0f4c70 100644
--- a/R/utility.R
+++ b/R/utility.R
@@ -69,6 +69,11 @@ get.encoded.distance <- function(points) {
 #' Any colors specified in `clone.colours` are maintained in the order
 #' specified and are used as the first colors for the `clone.ids`.
 #'
+#' if `clone.colours` is NULL or an empty vector, _and_
+#' `minimum.number.of.colours` is 0, `NULL` is returned
+#' so BPG's default color selection can be used without needing to
+#' check for `NULL`.
+#'
 #' @param clone.colours A vector of colors assigned to clones. If `NULL`, colors will be generated automatically.
 #' @param clone.ids A vector of clone identifiers.
 #' @param minimum.number.of.colours An integer specifying the minimum number of colors required.
@@ -89,7 +94,7 @@ get.clone.colours <- function(clone.colours, clone.ids, minimum.number.of.colour
             );
         }
 
-    if (!is.null(clone.colours)) {
+    if (!is.null(clone.colours) && !is.null(clone.ids)) {
         unique.clone.ids <- unique(clone.ids);
         sampled.colors <- sample(colors(), size = length(unique.clone.ids));
         sampled.colors[seq_along(clone.colours)] <- clone.colours;
@@ -109,6 +114,11 @@ get.clone.colours <- function(clone.colours, clone.ids, minimum.number.of.colour
 #' Any colors specified in `clone.colours` are maintained in the order
 #' specified and are used as the first colors for the `clone.ids`.
 #'
+#' if `clone.colours` is NULL or an empty vector, _and_
+#' `minimum.number.of.colours` is 0, `NULL` is returned
+#' so BPG's default color selection can be used without needing to
+#' check for `NULL`.
+#'
 #' @param clone.colours A vector of colors assigned to clones. If `NULL`, colors will be generated automatically.
 #' @param clone.ids A vector of clone identifiers.
 #' @param clone.order An optional vector specifying the order of clones. If `NULL`, clone order is not gauranteed.
@@ -120,7 +130,11 @@ get.clone.colours <- function(clone.colours, clone.ids, minimum.number.of.colour
 #'   \item{clone.order}{The ordered clones.}
 #' }
 get.clone.colours.in.order <- function(clone.colours, clone.ids, clone.order = NULL, minimum.number.of.colours = 0) {
-    if (is.null(clone.order)) {
+    if (is.null(clone.colours) && is.null(clone.order)) {
+        clone.ids <- NULL;
+        }
+
+    if (is.null(clone.order) && !is.null(clone.ids)) {
         unique.clone.ids <- unique(clone.ids);
         clone.order <- c(clone.order, unique.clone.ids[!unique.clone.ids %in% clone.order]);
         }
diff --git a/man/get.clone.colours.Rd b/man/get.clone.colours.Rd
new file mode 100644
index 0000000..ab6e9c5
--- /dev/null
+++ b/man/get.clone.colours.Rd
@@ -0,0 +1,29 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/utility.R
+\name{get.clone.colours}
+\alias{get.clone.colours}
+\title{Generate a named vector of colors for every clone ID specified.}
+\usage{
+get.clone.colours(clone.colours, clone.ids, minimum.number.of.colours = 0)
+}
+\arguments{
+\item{clone.colours}{A vector of colors assigned to clones. If `NULL`, colors will be generated automatically.}
+
+\item{clone.ids}{A vector of clone identifiers.}
+
+\item{minimum.number.of.colours}{An integer specifying the minimum number of colors required.}
+}
+\value{
+A named vector of colors assigned to each clone.
+}
+\description{
+Assigns colors to clones, ensuring a minimum number of colors are used.
+Any colors specified in `clone.colours` are maintained in the order
+specified and are used as the first colors for the `clone.ids`.
+}
+\details{
+if `clone.colours` is NULL or an empty vector, _and_
+`minimum.number.of.colours` is 0, `NULL` is returned
+so BPG's default color selection can be used without needing to
+check for `NULL`.
+}
diff --git a/man/get.clone.colours.in.order.Rd b/man/get.clone.colours.in.order.Rd
new file mode 100644
index 0000000..2d767c5
--- /dev/null
+++ b/man/get.clone.colours.in.order.Rd
@@ -0,0 +1,41 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/utility.R
+\name{get.clone.colours.in.order}
+\alias{get.clone.colours.in.order}
+\title{Generate a named vector of colors for every clone ID specified,
+ordered by the clone IDs in `clone.order`.}
+\usage{
+get.clone.colours.in.order(
+  clone.colours,
+  clone.ids,
+  clone.order = NULL,
+  minimum.number.of.colours = 0
+)
+}
+\arguments{
+\item{clone.colours}{A vector of colors assigned to clones. If `NULL`, colors will be generated automatically.}
+
+\item{clone.ids}{A vector of clone identifiers.}
+
+\item{clone.order}{An optional vector specifying the order of clones. If `NULL`, clone order is not gauranteed.}
+
+\item{minimum.number.of.colours}{An integer specifying the minimum number of colors required.}
+}
+\value{
+A list containing:
+\describe{
+  \item{clone.colours}{A named vector of colors assigned to each clone.}
+  \item{clone.order}{The ordered clones.}
+}
+}
+\description{
+Assigns colors to clones and ensures they follow a specified order.
+Any colors specified in `clone.colours` are maintained in the order
+specified and are used as the first colors for the `clone.ids`.
+}
+\details{
+if `clone.colours` is NULL or an empty vector, _and_
+`minimum.number.of.colours` is 0, `NULL` is returned
+so BPG's default color selection can be used without needing to
+check for `NULL`.
+}
diff --git a/tests/testthat/test-utility.R b/tests/testthat/test-utility.R
index aeb18c7..3b783dd 100644
--- a/tests/testthat/test-utility.R
+++ b/tests/testthat/test-utility.R
@@ -76,3 +76,163 @@ test_that(
 
         expect_equal(order(result), expected.order);
     });
+
+test_that(
+    'get.clone.colours returns expected vectors', {
+        result <- get.clone.colours(NULL, NULL);
+        expect_null(result);
+        result <- get.clone.colours(NULL, c('ABC', 'DEF'));
+        expect_null(result);
+        result <- get.clone.colours(c('red','green'), NULL);
+        expect_null(result);
+        result <- get.clone.colours(c(), c());
+        expect_null(result);
+        result <- get.clone.colours(NULL, c());
+        expect_null(result);
+        result <- get.clone.colours(c(), NULL);
+        expect_null(result);
+        result <- get.clone.colours(c(), c('ABC', 'DEF'));
+        expect_null(result);
+        result <- get.clone.colours(c('red', 'green'), c());
+        expect_null(result);
+        result <- get.clone.colours(c('red','green'), c('ABC','DEF'));
+        expect_equal(result, c(ABC = 'red', DEF = 'green'));
+        result <- get.clone.colours(c('red'), c('ABC','DEF'));
+        expect_equal(names(result), c('ABC', 'DEF'));
+        expect_true(result['ABC'] == 'red');
+        expect_true(!is.na(result['DEF']) && nzchar(result['DEF']));
+        result <- get.clone.colours(c(NULL,'red'), c('ABC','DEF'));
+        expect_equal(names(result), c('ABC', 'DEF'));
+        expect_true(result['ABC'] == 'red');
+        expect_true(!is.na(result['DEF']) && nzchar(result['DEF']));
+        result <- get.clone.colours(c('red',NULL), c('ABC','DEF'));
+        expect_equal(names(result), c('ABC', 'DEF'));
+        expect_true(result['ABC'] == 'red');
+        expect_true(!is.na(result['DEF']) && nzchar(result['DEF']));
+        result <- get.clone.colours(c('red','green'), c('ABC'));
+        expect_equal(result, c(ABC = 'red'));
+        result <- get.clone.colours(c('red','green'), c(NULL,'ABC'));
+        expect_equal(result, c(ABC = 'red'));
+        result <- get.clone.colours(c('red','green'), c('ABC',NULL));
+        expect_equal(result, c(ABC = 'red'));
+    });
+
+test_that(
+    'get.clone.colours returns expected vectors with minimum colours specified', {
+        result <- get.clone.colours(NULL, NULL, 3)
+        expect_null(result);
+        result <- get.clone.colours(c('red', 'green'), NULL, 3)
+        expect_null(result);
+        result <- get.clone.colours(c('red'), NULL, 3)
+        expect_null(result);
+        result <- get.clone.colours(c('red', 'green'), c('ABC','DEF'), 3)
+        expect_equal(result, c(ABC = 'red', DEF = 'green'));
+        result <- get.clone.colours(c('red'), c('ABC','DEF'), 3)
+        expect_equal(names(result), c('ABC', 'DEF'));
+        expect_true(result['ABC'] == 'red');
+        expect_true(!is.na(result['DEF']) && nzchar(result['DEF']));
+        result <- get.clone.colours(c('red', 'green'), c('ABC'), 3)
+        expect_equal(result, c(ABC = 'red'));
+    });
+
+test_that(
+    'get.clone.colours.in.order returns expected vectors when order is not specified', {
+        # get.clone.colours.in.order has same result as get.clone.colours
+        # with the change that a named list is returned with two members
+        result <- get.clone.colours.in.order(NULL, NULL)
+        expect_true(setequal(result, list(clone.colours = NULL, clone.order = NULL)))
+        result <- get.clone.colours.in.order(NULL, c('ABC', 'DEF'))
+        expect_true(setequal(result, list(clone.colours = NULL, clone.order = NULL)))
+        result <- get.clone.colours.in.order(c('red','green'), NULL)
+        expect_true(setequal(result, list(clone.colours = NULL, clone.order = NULL)))
+        result <- get.clone.colours.in.order(c(), c())
+        expect_true(setequal(result, list(clone.colours = NULL, clone.order = NULL)))
+        result <- get.clone.colours.in.order(NULL, c())
+        expect_true(setequal(result, list(clone.colours = NULL, clone.order = NULL)))
+        result <- get.clone.colours.in.order(c(), NULL)
+        expect_true(setequal(result, list(clone.colours = NULL, clone.order = NULL)))
+        result <- get.clone.colours.in.order(c(), c('ABC', 'DEF'))
+        expect_true(setequal(result, list(clone.colours = NULL, clone.order = NULL)))
+        result <- get.clone.colours.in.order(c('red', 'green'), c())
+        expect_true(setequal(result, list(clone.colours = NULL, clone.order = NULL)))
+        result <- get.clone.colours.in.order(c('red','green'), c('ABC','DEF'))
+        expect_true(setequal(result,list(clone.colours = c(ABC = 'red',DEF = 'green'), clone.order = c('ABC','DEF'))))
+        result <- get.clone.colours.in.order(c('red'), c('ABC','DEF'))
+        expect_equal(names(result), c('clone.colours', 'clone.order'))
+        expect_equal(names(result$clone.colours), c('ABC', 'DEF'))
+        expect_true(result$clone.colours['ABC'] == 'red')
+        expect_true(!is.na(result$clone.colours['DEF']) && nzchar(result$clone.colours['DEF']))
+        expect_equal(result$clone.order, c('ABC','DEF'))
+
+        result <- get.clone.colours.in.order(c(NULL,'red'), c('ABC','DEF'))
+        expect_equal(names(result), c('clone.colours', 'clone.order'))
+        expect_equal(names(result$clone.colours), c('ABC','DEF'))
+        expect_true(result$clone.colours['ABC'] == 'red')
+        expect_true(!is.na(result$clone.colours['DEF']) && nzchar(result$clone.colours['DEF']))
+        expect_equal(result$clone.order, c('ABC','DEF'))
+
+        result <- get.clone.colours.in.order(c('red',NULL), c('ABC','DEF'))
+        expect_equal(names(result), c('clone.colours', 'clone.order'))
+        expect_equal(names(result$clone.colours), c('ABC','DEF'))
+        expect_true(result$clone.colours['ABC'] == 'red')
+        expect_true(!is.na(result$clone.colours['DEF']) && nzchar(result$clone.colours['DEF']))
+        expect_equal(result$clone.order, c('ABC','DEF'))
+
+        result <- get.clone.colours.in.order(c('red','green'), c('ABC'))
+        expect_true(setequal(result,list(clone.colours = c(ABC = 'red'), clone.order = c('ABC'))))
+        result <- get.clone.colours.in.order(c('red','green'), c(NULL,'ABC'))
+        expect_true(setequal(result,list(clone.colours = c(ABC = 'red'), clone.order = c('ABC'))))
+        result <- get.clone.colours.in.order(c('red','green'), c('ABC',NULL))
+        expect_true(setequal(result,list(clone.colours = c(ABC = 'red'), clone.order = c('ABC'))))
+    });
+
+test_that(
+    'get.clone.colours.in.order returns expected vectors when order is specified', {
+        # get.clone.colours.in.order with order specified
+        result <- get.clone.colours.in.order(NULL, NULL, c('DEF','ABC'))
+        expect_true(setequal(result, list(clone.colours = NULL, clone.order = c('DEF','ABC'))))
+        result <- get.clone.colours.in.order(NULL, c('ABC', 'DEF'), c('DEF','ABC'))
+        expect_true(setequal(result, list(clone.colours = NULL, clone.order = c('DEF','ABC'))))
+        result <- get.clone.colours.in.order(c('red','green'), NULL)
+        expect_true(setequal(result, list(clone.colours = NULL, clone.order = NULL)))
+        result <- get.clone.colours.in.order(c(), c(), c('DEF','ABC'))
+        expect_true(setequal(result, list(clone.colours = NULL, clone.order = c('DEF','ABC'))))
+        result <- get.clone.colours.in.order(NULL, c(), c('DEF','ABC'))
+        expect_true(setequal(result, list(clone.colours = NULL, clone.order = c('DEF','ABC'))))
+        result <- get.clone.colours.in.order(c(), NULL, c('DEF','ABC'))
+        expect_true(setequal(result, list(clone.colours = NULL, clone.order = c('DEF','ABC'))))
+        result <- get.clone.colours.in.order(c(), c('ABC', 'DEF'), c('DEF','ABC'))
+        expect_true(setequal(result, list(clone.colours = NULL, clone.order = c('DEF','ABC'))))
+        result <- get.clone.colours.in.order(c('red', 'green'), c(), c('DEF','ABC'))
+        expect_true(setequal(result, list(clone.colours = c(DEF = 'red',ABC = 'green'), clone.order = c('DEF','ABC'))))
+        result <- get.clone.colours.in.order(c('red','green'), c('ABC','DEF'), c('DEF','ABC'))
+        expect_true(setequal(result,list(clone.colours = c(DEF = 'red',ABC = 'green'), clone.order = c('DEF','ABC'))))
+        result <- get.clone.colours.in.order(c('red'), c('ABC','DEF'), c('DEF','ABC'))
+        expect_equal(names(result), c('clone.colours', 'clone.order'))
+        expect_equal(names(result$clone.colours), c('DEF', 'ABC'))
+        expect_true(result$clone.colours['DEF'] == 'red')
+        expect_true(!is.na(result$clone.colours['ABC']) && nzchar(result$clone.colours['ABC']))
+        expect_equal(result$clone.order, c('DEF','ABC'))
+
+        result <- get.clone.colours.in.order(c(NULL,'red'), c('ABC','DEF'), c('DEF','ABC'))
+        expect_equal(names(result), c('clone.colours', 'clone.order'))
+        expect_equal(names(result$clone.colours), c('DEF','ABC'))
+        expect_true(result$clone.colours['DEF'] == 'red')
+        expect_true(!is.na(result$clone.colours['ABC']) && nzchar(result$clone.colours['ABC']))
+        expect_equal(result$clone.order, c('DEF','ABC'))
+
+        result <- get.clone.colours.in.order(c('red',NULL), c('ABC','DEF'), c('DEF','ABC'))
+        expect_equal(names(result), c('clone.colours', 'clone.order'))
+        expect_equal(names(result$clone.colours), c('DEF','ABC'))
+        expect_true(result$clone.colours['DEF'] == 'red')
+        expect_true(!is.na(result$clone.colours['ABC']) && nzchar(result$clone.colours['ABC']))
+        expect_equal(result$clone.order, c('DEF','ABC'))
+
+        result <- get.clone.colours.in.order(c('red','green'), c('ABC'), c('DEF','ABC'))
+        expect_true(setequal(result,list(clone.colours = c(DEF = 'red',ABC = 'green'), clone.order = c('DEF','ABC'))))
+        result <- get.clone.colours.in.order(c('red','green'), c(NULL,'ABC'), c('DEF','ABC'))
+        expect_true(setequal(result,list(clone.colours = c(DEF = 'red',ABC = 'green'), clone.order = c('DEF','ABC'))))
+        result <- get.clone.colours.in.order(c('red','green'), c('ABC',NULL), c('DEF','ABC'))
+        expect_true(setequal(result,list(clone.colours = c(DEF = 'red',ABC = 'green'), clone.order = c('DEF','ABC'))))
+    });
+