Reference Cinema 4D Basic Features BodyPaint 3D Image Menu
Function available in CINEMA 4D Prime, Visualize, Broadcast, Studio & BodyPaint 3D

Convert to RGB

You can use this command to convert the active texture from grayscale (8bits) to RGB (24-bits). Convert To RGB will not restore color to a black-and-white image, but it does enable you to paint colors on the channel.