What to use to get blue toilet bowl cleaner out of floor grout?

Try making a paste with baking soda and hydrogen peroxide

What color is the grouting originally? If it is white, than you should be O.K. with the hydrogen peroxide, or regular bleach.

Wear gloves, as both will dry out your hands, and apply to the grout lines with a narrow paintbrush. Let sit before wiping off. Depending on how porous your grouting is, than you may need to scrub a bit after it sits, and it may need more than one round of treatment.

I would try Dollar Tree Awesome Orange in the half gallon. I have a clients whose shower and tub are both blue everytime I go there, and previously I tried everything to remove it, but this stuff just melted it off. Use a brush if its stubborn.

I used Concrobium mild stain eraser powder. It needs to be diluted however after scrubbing relentlessly I placed a bit of the powder on the grout and scrubbed with a bit of water …. Left for couple hours .. and overnight. It’s all gone! All of my grout around the toilet was vibrant blue. Hopegully you can see the pic below. Never ever again blue bleach tablets!!