This is a porous tile and the talcum powder has gotten into the "pores" and will probably need to be scrubbed lightly with a brush. I would suggest using a mild dish washing product (like Dawn) mixed in water and scrub gently, dry and wait to see results before trying something else.
Murphy Oil Soap is recommended because it's very close to pH neutral. Dilute 1/4 cup in a gallon of warm water and scrub the area well. Rinse and dry. never use paper towels to dry.
Don't waste your time washing the tiles! Talcum powder does not dissolve in water. It is a mineral, more precisely it is hydrated magnesium silicate with most of the time, traces of other metals like nickel, iron and aluminum, nothing that you will dissolve with water. Let it dry and use a powerful vacuum cleaner only.
I would use Oxiclean Versitle powder to clean the tiles. Or use hydrogen peroxide on the tiles.
Mr Clean Magic Eraser does a good job with minimal effort.