<?php
declare(strict_types=1);

namespace XX\XXX;

use XX\XXX\Structs\Attribute\ArrayList;

class Ball
{
    #[ArrayList('balablub')]
    public array $colors = [];
}

<?php
declare(strict_types=1);

namespace XX\XXX;

class Example
{

    public function readArgumentValue(): void
    {
        $reflection = new \ReflectionClass(Ball::class);
        $reflectionProperties = $reflection->getProperties();
        $reflectionProperty = $reflectionProperties[0];
        $reflectionAttributes = $reflectionProperty->getAttributes();
        $reflectionAttribute = $reflectionAttributes[0];
        $reflectionArguments = $reflectionAttribute->getArguments();
        $reflectionArgument = $reflectionArguments[0]; // balablub
    }
}