Wow that is very interesting! The orange color appears in clean glassware as well. I was told that a basic solution can polymerize acetone creating a yellow/orange color. The haloform reaction could provide the base and of course the chloroform (RCOCH3 + 3NaClO -> RCOONa + CHCl3 + 2NaOH)... but acetone is a "dimethyl ketone" so I'm not sure that equation is completely right.
I don't think it gets quite hot enough to create phosgene (at least I hope not)! But I always do this in the fume hood and would suggest the same to anyone else who wants to clean their dirty glassware by this method (works great on Al-salts from AlMe3, DIBAL-H, etc.)!