In the original designs, each turtle has three fingers and two toes, based on characters created by Kevin Eastman and Peter Laird.
A deviation from its previous incarnations was seen in the Teenage Mutant Ninja Turtles 2012 TV series (developed by the Nickelodeon Animation Studio) where they have three toes on each foot instead of two.
Teenage Mutant Ninja Turtles premiered in May, 1984 at a comic book convention held at a local Sheraton Hotel in Portsmouth, New Hampshire. It was published by Mirage Studios in an oversized magazine-style format using black & white artwork on newsprint, limited to a print run of only 3,000 copies.
When it comes to their colors, Thomas Wheeler, writing for MasterCollector.com, says:
The Turtles are all slightly different shades of green, as well. This has long been established in the toy line. Traditionally, Raphael has always been the darkest green of the lot, but that's not really the case here. Of the four, Michaelangelo is the darkest. Leonardo and Donatello are virtually identical, although Donatello might be fractionally lighter. Raphael is, as best as I can put it, very slightly darker and just a tad more gray-green than Leo and Don, without being nearly as dark a green as Mike.
Of interest, check out The Complete History of Teenage Mutant Ninja Turtles shared by Mental Floss.