I made this graphic of default R21 COLOR Constants as a guide for me to find the right colors and wanted to share it with the community:
The spaces where there is no text means that the attribute is the same as
c4d.COLOR_BG and is blending in with the background.
Also, while making this, I found that the documentation lists one attribute that throws an error:
AttributeError: 'module' object has no attribute 'COLOR_TIMELINE'