Check out this post. I've painted a couple of tile fireplace surrounds, but not the floor. But I believe the process is the same. You can get grout refresh to change the color of your grout (basically painting over it). https://jessicawellinginteriors.com/faux-cement-tile-fireplace/
Take a good photo or a leftover piece of tile if you have one to the paint department of your home improvement store and ask for their suggestions. They know what to use.
Alma, this really works! Whenever I have a question about flooring, cabinets, window treatments, etc,, I always see what the home improvement stores are selling and displaying. They are up to date on the latest materials, application tools and trends and are so knowledegable!
There are lots of posts here that can help you: