When I read the title of your post I had an idea, it is possible to load paper into a printer the wrong way round believe it or not. The heat of the printer causes the paper to roll - remember it is kept on large rolls before it is vut to A4 et al size - and jam.
Since the problem only occurs with colour printing it might be that the extra heat - from more use of the laser - is causing the paper to roll. I would suggest you ether take the paper out and put it in the other way up, or use some different paper.
I do not think the toner would be to blame, unless it is a cunning ploy by Epsom to force everyone to use its own toners.
Well maybe someone that knows more will be more helpful.