Mikey;
If you have tried two reducing agents to the point of color loss . . .
then I would try an oxidizer w/enzyme on the stain.
Our Odor Attack powder with a powerful UV light does the best job on mustard . . .
which is a strong yellow dye.
Test carpet with mustard stain ( lower left corner) removed by carpet cleaners using that technique:
Bottom two after UV + oxidizer spotting:
Larry