Thanks stampede! Both suggestions have proven very useful.

Moving the enum to be before the #defines worked so that I could simply #include the namespace from within any of the files relying on the enums defined within the namespace, while still allowing an end user to #include "color_namespace.h" and maintain full functionality of every feature.

Separating the enum definition into another header to keep things clean also worked, but it meant that I had to #include multiple files instead of just one.