Which product works the best for cleaning tile grout?

I have tried two different products and it seems hopeless, the one is a foam and it changes colors when it is “activated” and you are just supposed to wipe it off and the grout be spotless, but sadly not the case, another one was scrub and bubbles and it was also a foam, I waited 3 minutes and wiped, but nothing. Is there no product that can actually do what its supposed to do and remove that yellow stuff in between the tiles?