Can i use artist acrylic paint on grout on bathroom floor

It would be easier to re-grout with the color of your choice.

try a small area where you have a lot of traffic . soon after you paint it when it's dry

i put 3 coats of floor Wax. Seems to work well for me.

nope, the paint won't hold up -- I'd stain the grout a dark contrasting color -- if the tile is 'white' then black or coffee brown - if it's a decorated grout, I'd use an associated color, but dark ... and seal.

I painted grout in my old kitchen with Walmart's acrylic. Make sure you clean well. To ensure it not washing off (it soaks in, doesn't come off easily) you can deal it with a sealer pen. I didn't do this, just touched up areas with extra paint. The floors looked new.