Hello, I have personally not done this exciting refurb project —but here’s a few links that might be helpful.
You didn't mention if you have ceramic tile or regular floor tiles but if you're asking about ceramic tile, I've saved these article to help. Just remember that the preparation is very important and make sure that you do every step. Wishing you the best.
Paint Ceramic tile floors
From experience, just realize paint just sits on tile. You need to be very careful with it. If doing inside shower area it lasts less longer due to heavy use and water. If it gets scratched it will peel. Good option to buy time to save up for replacement . A friend did her guess bath and it looked good for 6 years. Did the master bath, only lasted 1 1/2 years.
Rather than painting my tile I used these floor decals and love them! https://thehoneycombhome.com/floor-stickers-in-the-bathroom/