Well, if you're going to be paying out the arse for color copies you definetly do NOT want to have some web site do it for you.
I do Copy Center over at Staples and having done plenty of color copy orders, you do want to see a sample of what it will look like before you go off and do 250+ copies of it. You may need to change the paper type, saturation, color balance, etc etc to get it to match the original. If you could care less what it looks like as long as it's in color then go ahead with the online site but it's risky.