w/y phonotactics

[chromonym]

Formatives and modular adjuncts with Aspect+FAC/CCN and dual referential adjuncts all allow the option of using -y- in place of -w-.
While I couldn't find anything about this in the documents, I should probably add a check for what the preceding (and maybe following) vowel is and decide on -w- or -y- based on what it is (to avoid -uw- and -iy-).