I can change cuffs and collar-but their doesn't appear to be a way that turnbacks change in artillery- even though color selection is presented on the left of the uniform figure in the OoB. Not a show stopper-I just did a search in the forum and it appears it was an issue a while back.
Looked through the game files and I couldn't find a file to edit or modify to get this done or change uniform in game. Unit is listed in OoB save but no color selection to edit.
I'm patched up to 2.3X1