Well that's an important one - did you think you might ask them? Were you really afraid?
I have always been told to take medications regularly even with a colonoscopy.
I've been told to take all my medicines even day of scope although I wasn't on anything like Pentasa/Asacol (never been on Asacol actually), if it has the little pellet like stuff that Pentasa does then I think it might be wise to avoid it day of just so you don't get all the little grains in there .. not that it would do any harm I suppose. I just recall being on a liquid diet when I was obstructed and taking Pentasa and was pooping the little pellets out.
Before your colonoscopy, unless your doctor tells you otherwise, I'm pretty sure you're supposed to take your medication with a small sip of water. However, this is not a stupid question so you shouldn't be afraid to ask it. In fact, I feel fairly strongly that there is no stupid questions when it comes to Chrons!
I have images of one of my scopes with an asacol tablet clear as day in it, you could almost ready the writing on it. MY GI said take them with a small sip of water.