Changing the font size will probably solve your problem.
I have had no page turn problems since updating to firmware 1.4.3. It is too soon to be sure, but it looks like they solved the page turn problem in 1.4.3.. So you might consider to do a manual update to 1.4.3..
This is a problem with the Nook. The images are too big for the screen and the Nook is too dumb to resize them. I don't think it has anything to do with the fact that they are color. That is, the publisher of the ebook didn't customize the contents of the book for the Nook. So I think you're out of luck there. The getting stuck turning the pages back is as noted a well-known bug in the Nook which happens when an image is tall relative to the display size, so when it calculates where to start re-drawing the previous page, it sees there's still some image left, so it goes and gives you that same image again. Changing the font size or toggling off publisher defaults seems to be a useful workaround.