Just noticed this problem in SU 2017. It’s quite simple to replicate.
Create a Color based material (as opposed to a texture based material).
Paint a surface with it.
Paint a surface with the duplicate material.
Sketchup uses the first material with the same color and totally ignores the newly created duplicate color with a different name.
This breaks my render engine (Thea Render).
This is also a general organizational nightmare because materials (faces) need to have names (or some kind of meta data) associated with them even if they are the same color to note unique surface properties (like eggshell, gloss, etc.)
Please tell me how this can be fixed!