I vote no for colors in IC, and I'd also rather people stuck with the standard font and used bold/italics consistently and sparingly. Pressing enter and tab before switching speaker makes the dialog visually distinct enough. 
	- Colors tend to be distracting, and since I have rather hue- and contrast-sensitive eyes, most colored text tends to be physically unpleasant to read. It's slightly less relevant on dark background, but coupled with light background I most likely have to skip reading or only skim-read it unless I actually have the incentive to open up a separate plain text editor and copy the entire post over there to read it, each and every time...