Grout re-colorant suggestion?

I've got some 8 year old sanded bathroom floor grout that started out white but has gotten dingy over the years. It's 1" hexagon tile so it would be impossible to scrub all those lines.

What's a good brand and product for recoloring my grout back to white? It's been a while since I've looked into grout cleaning products and I'm guessing there's newer technologies out there I'm not aware of.

Thanks!