One mic through two pres wouldn't give you stereo the way two mics would, but you knew that. Using one clean pre and one color pre on the same mic could be educational, but you should be doing that with your shootout files, so that when it's time to do the session, you know the characteristics of your pres and you choose accordingly.
Many would suggest, when in doubt, go with the clean pre. You can always add character later with plugins in the mix, but you can't undo distortion, and distortion is what 'colored' pres are all about. An example: tube mics. Many mid-level tube mics already are distorting a bit. Run it through a clean pre and you actually get to hear what the mic sounds like. Run it through a colored pre, and your 'S's turn to crap, which is really hard to fix.