I have been trying to export a model with vertex colors, from a blender model to FBX. (And then to Roblox) But, I cant seem to find the export with vertex colors in the FBX export dialog.
This person said that there was a property, but I cant find it.
If you want to use simple colors instead of textures, you can use Vertex Paint mode and color your model using this method. Roblox can import vertex colors contained in your model (if not, make sure you have ticked export vertex colors in the FBX/OBJ exporter dialog in Blender).