Lots of ideas here
Hello, I have personally not done this fabulous refurb project —but here’s a few links that might be helpful.
You want to paint the entire floor with grout or you want to paint the grout lines in the tiled floor?
Use a Brick and Tile paint, available at the DIY store.......
Tile paint as mentioned above for the tile itself. For the grout, you can use either grout paint or exterior paint. Make sure you seal once the job is finished.