Is enriched pasta OK to eat before having a colonoscopy?

For any colonoscopy, you must spend one full day with no solid food of any kind, the day before the procedure (Jell-O works to fill the gap, though). But prior to that day of fasting, you can pretty much eat normally.

To be honest it depends a lot on the protocol of the hospital that you're with. Some hospitals specify only "clear fluids" for three days before a colonoscopy, and laxatives, whereas other hospitals' specify a normal diet, with a lot of laxatives the day beforehand. It's best to consult your gastroenterologist, or the information that you were (probably) provided with pre-investigation, to find out what the protocol is.

One of the most commonly followed procedures today is nothing but clear liquids a full day before (Jello qualifies as a "clear liquid") and beginning about 4 PM that day, the ingestion of a half-gallon of Mirilax, which has no taste. The procedure is constantly being improved and modified to make it easier for all concerned, but the procedural directives for the place where yours will be done are the ones you should follow.