So, it finally occurred to me that almost all the canvases I do use the same set of symbols, mainly numbers 1-9 and many of the same letters. I stopped writing the color number on each label and just put the symbols on it. Now I don't have to peel off the labels between kits as I have a set of trays already labeled with all the symbols I need.
I have had the occasional kit that uses weird symbols instead of numbers/letters so will have to label additional trays when I next come across one of them. However, kitting up is so much less annoying when it is just dumping the old drills and putting the new ones in the trays.
I feel kind of dumb for not realizing this sooner!