ELISA calls for help

[WS]

Dear Philip,

which dye(s) would you recommend for scrutinizing pipetting? Anything
that is yellow (for OD450) or do you have a personal favorite for
aqueous solutions?
Actually, I don't want to cook TMB with peroxidase and add acid, just
to be as close as possible to the original. The purpose I want to use
it for is calibrate a homemade pipetting robot for microplates. It's
for TMB based ELISAs

Thanks!

Wolfgang