I knew you were going to ask that! 😀 Forgive me because it's been nearly a year but I believe I used the "copy" feature to create a copy of the surface I wanted to add color to, changed it's color in the view tab and then used that in my drawing. I exported the drawing as a color pdf, just the surface(s) I added color to appeared in their specified colors and the vendor was able to easily discern which surface to apply finish to. I'll see if I can find the model/drawing I did this to but it's been forever and I don't remember the P/N. Good luck!
P.S. After finding the model/drawing I was referring to. In my case, we need the part produced in 3 separate colors so I ended up creating a family table with each color as a member. I copied every surface, pasted them over the part and then I was able to add color to each family table member individually so it would show up on the print. Hope that helps.
