Tilex, bleach, soft scrub with a scrub brush. Once cleaned be sure to seal
I like Baking soda and hydrogen peroxide combined with good old fashioned hands and knees scrubbing. A good sealing with a quality grout sealer post clean will keep it looking fresh for a few years or more with excellent home cleaning on a weekly basis as well as a shoes off policy. My last period for my entry hall was Spring 2012 to November 2018 using the above combination in my rainy Seattle home.
clorox cleanup scrub brush if not paint the grout with a tiny brush it comes nice