I use whatever color matches or contrasts with the fabric. Otherwise, I don't pay much attention to the thread name, just use whatever is in my thread box. I have, however, removed the threads that are on wooden spools and am keeping them for crazy quilting where lots of different ones are used. That way no one spool will be essential to the structural safety of the lap robes.
The wooden spools are much older than the more modern plastic holders and I'm not too sure they are worthy of using in a kids' much loved and much washed lap quilt.