Ccanning and printing from a color printer may be the cheapest way to get color copies if you merely want a few color copies of an old photograph or a photograph that you don't have the negative for, or a test brochure or flyer. Even if you don't have a scanner and color printer, chances are there is one available at work or at a friend's house.
Buying in bulk from a local printer may be the cheapest way to go if you need a lot of color copies. Call some local printers and get bids in order to get the best deal. Be sure to include other things they might need when asking for a bid such as folding as with brochures, or three-hole punched sheets. Otherwise the bid will not include these services and the overall cost will be more. The cost of delivery should also be factored in, unless you plan to pick up the copies yourself.
Buying color copies in bulk online can be cheaper and more convenient to buying color copies from a local printer, because in some cases online printers offer free shipping and even free extra copies. Also, you can order from the comfort of your computer and have the copies delivered, eliminating the need to go and pick them up.