Good morning, i will be starting my colonoscopy prep tomorrow. can i use a small amount of 2% milk in early morning coffee, then start my clear liquid?

Sure: That amount won't make any difference. But I'm a little concerned that bending this "rule" may lead you to bend a few more. Improper or inadequate prep for a colonscopy is the biggest reason many have to be repeated because the exam was suboptimal/inconclusive. You wouldn't want to repeat it. I would strongly encourage you to follow the prep instructions PRECISELY. It's one day:)