I have been having a lot of trouble getting materials to show up, not just in solid view, but at all. I have gone through a large number of versions of this file and thought maybe something got screwed up somewhere along the way, so I deleted all the materials and started rebuilding them. But the problem shows signs of returning, as now one material is visible in solid view, but as I create more they are only visible in material or render view. They are just basic flat colors.
I don't know a lot - I've been switching back and forth between Blender and Cycles Render as I've been building this. Could that be the issue?