Mirage Studios' Teenage Mutant Ninja Turtles #1 was published, in all its black and white glory, in 1984. For such a foundational comic, it's no surprise companies have taken any excuse they can to reprint it. Often that excuse involves coloring the formerly grayscale art.
Fun fact: it's possible to tell different printings of this issue apart by the way the shading is done, with Page 33 being a great example. Is there shading in the background of the panels, or are they blank? Is that marker behind Leonardo, or zipatone? The one seen here is the original first printing.
In 1986, First Comics got the rights to reprint TMNT in color. Rather than going one issue at a time, they did collections, so Teenage Mutant Ninja Turtles: Book I included the first three issues of the comic plus two new short stories. The new colors for issue #1 in the collection were done by Kevin Eastman himself, making them as close to "official" as you can get. (Shredder's first appearance in color was September of 1985, on the wraparound cover of the fourth printing of TMNT #1, and these colors matched those.)
Other than choosing to make the sword strike white, like an impact effect instead of a wound, this is nice work. The brownish-green used for the Turtles is a better hue than bright green, and the variety of colors in the backgrounds of the panels makes the page "pop."
That TPB was released in 1986, and it would be 2009 before the boys escaped black-and-white again. Just before Peter Laird sold the Turtles to Viacom, Mirage released TMNT Full Color #1, with colors by Steve Lavigne.
Shredder's darker, but still maroon, and the blood looks like blood now. The speed lines behind Leo are a smart addition, but every background being glowy green flattens the action out. It's a bit too "digital" for a comic from the '80s; everything looks weirdly smooth.
2012 saw IDW publish TMNT Color Classics, which was intended to cover the entire run of comics, one month at a time. There's no individual colorist credited, just "Tom Smith's Scorpion Studios." Whether that's Tom working by himself under a business name or it's an entire team of people, this is where Blue Shredder comes from.
While still colored on a computer, this one looks better because it looks like it was just dropped right over the original art, giving everybody blemishes and imperfections the 2009 attempt airbrushed away. The backgrounds still look out of place, since they're just color gradients over empty space, but the rest is good. Other than the inexplicable choice to make Shredder blue. Beyond the color, his bare arms are colored like sleeves now, and you'll notice he's even got gloves here, something that changes from page to page (suggesting Scorpion Studio is in fact a team of people and not just one), and something the toy chose to ignore.