I did a little research for you on the LA website. This is what I've found. There is a product called Sew Clean that is a natural cleaner that is good for many things. Several report good results in getting out the yellow.
The problem is that this chalk has wax in it, and it's made to be hidden in dressmaker interiors. They reported not to use the yellow, red or pink chalks, but several have had OK luck using the white (assumed it has less chalk?). Still, most dump out the chalk that comes in the little liners and refill with Miracle Chalk as they like the little holders (and this is what I'm gonna do too!).
Sorry it's not much help - I'll keep looking for homemade ideas.
Debbie in Austin