When I got the short on gray/yellow, I had not removed a sidemarker light (just the right front parking light, not realizing the side marker was illuminated... thought it was just a reflector). Disconnecting that bulb, I think gray/yellow is fine.

To test which circuit is causing the overload, I can remove the light switch and jump blue/red wire to either gray/yellow or gray/black and see which one blows the fuse next time (assuming I cannot repeat the chime causing the problem).

Going to drive to work today with headlights on to give it a long test. Will mess with it more tonight.

Thanks again for everybody's help!