How do you change tile grout color?

You can get grout stain. It will let you make it darker. If you want to change the grout altogether then it can be easily removed, but time consuming. Simple grout removal tools are available at local home stores. Also a oscillating multifunction power tool will make quick work of it. Then re-grout the joints in whatever color you choose. Grout charts are available where grout is sold. Remember grout will look darker when being installed and will dry lighter. Be very careful of making sure everything is clean. Vacuum out old joints with a wet/dry shop vac. If you use a power tool to remove grout have someone follow behind it with a shop vac. Or you will have dust everywhere.