Go to Rit's site and look at the color chart to see what's closest to what you want.
ColoRit Color Formula Guide | Rit Dye
Be sure to read their dyeing instructions. You'll probably need to pick up an industrial detergnet to get all the scotch guard out of the tabi so they'll take dye. You can get that at several places. I use
Dharma Trading Co. Homepage
Lots of helpful info on dyeing fabric there as well.
This should be a fairly straightforward project.