firstly, huge thanks to DustinOliver for letting me use their white eyes mod as a base to work from: 
https://www.nexusmods.com/tmntshreddersrevenge/mods/10?tab=posts 
seriously, this saved so much work.  great mod, check it out.

so i've made a handful of Splinter colors you can try out. You have your choice
of a full black and white (even many effects), red-robed Mirage inspired,
2k3 colors (and an alternate version with some effects changed to orange,
and two based on the first movie (plus a bonus one). Some effects will
still appear default, and I didn't do any of the hud/menus/cutscenes. 
Feelfree to sample the colors here and do that if you really like one.

Oh right, I don't think I bothered to change the frozen sprites on these,
so he'll appear vanilla when frozen. I may come back to that later.

There is an included color separated version you can use to shortcut
making your own mods as well. I may eventually separate out the trim
on his robe, but that seems like a lot of effort, so if anyone else wants to
do that feel free and let me know.

manual method:

to use this, decompress the archive and pick one file, and rename it to SplinterTexture.png

go to the folder TMNT\Content\2d\Animations\Players\Splinter

put the file you renamed in that folder
rename SplinterTexture.zxnb to something else (add a .old or .bak or something
and you can rename it back later to revert to standard)

Custom Skins method:

install both of these
https://www.nexusmods.com/tmntshreddersrevenge/mods/68
https://www.nexusmods.com/tmntshreddersrevenge/mods/70

unzip to the mods folder

enjoy, hopefully