I thought that when you selected 2 meshes and did a union on them, they each retained their own material. This does not seem to be working for me. Did I remember incorrectly? Is there some trick to doing this?
reap
odd behavior seems to be limited to text. I made text, converted it to a curve, converted it to a mesh and then union-ed them. Text loses color.
… hrmmm… not limited to text afterall… happens on some objects as well