I saw this topic discussed in the section on keyboard pictures. (I really must take pictures of my keyboards; I'm scared, though, that they might be used to defraud people on eBay.)
The ATTN key on a 2741 was not red, and IBM usually didn't go in for colorful keys, so most 3277 and 3278 display stations didn't do that either as far as I know. But I have seen ASR 33 and ASR 35 Teletypes with a red Break key.
Since the red key is used to interrupt a running program, I would think you would want a red Pause/Break key on a PC keyboard, not a red Esc key.
Of course, I do have some pretty strange ideas of the color scheme I would like to see on a keyboard, as a drawing on my web site illustrates:
Since it's only a drawing and not a picture, I figure this is the better thread for it.