Even the glitzy Plastic Logic device will come out only in black and white. I'll bet comics would look better on it than on Kindle, because of the larger screen, but still, they will loose something in black and white. Besides, comics readers are often also collectors, and with Kindle, all you collect is a pile of bytes. And will the mobile business traveler that is PL's target audience overlap the comic book market?
Time will tell. Of course, time will also bring color screens.