Best Practices for Painting Tile
Stick with vertical surfaces: It is not standard practice to take a roller to your kitchen or bathroom floor tile. Paint on horizontal tiled surfaces that receive traffic will soon wear off. Tile paint works best on vertical surfaces that receive less abuse, including backsplashes, wall tile, and wainscot tile.
Scuff the surface: Fine-grit (400 grit or higher) sandpaper is sufficient for deglossing the tile prior to painting. Your aim is not to completely remove the gloss to the base material but to bring down the gloss so the tile is no longer shiny. This helps the paint to adhere better.
Clean thoroughly: Because tile tends to be installed in areas that receive a lot of soap scum, food splatter, and other kitchen and bathroom debris, you must thoroughly clean the tile before painting. If the tile is very dirty, you might even need to clean it before sanding and then clean once more after sanding. Pressure washing your tile is an option to get it clean enough for painting.
Opt to paint the grout: Not only can you paint tile grout, but it is nearly impossible to avoid painting the grout. Masking off grout is difficult to do effectively for a clean look. However, you never should paint over any flexible areas, such as caulking or silicone seams.
Realize painting might not be a long-term solution: View painting tile as a treatment that might eventually wear down. Whether six months or six years from now, the paint will begin to flake and chip. Painting is a quick and low-cost way to freshen up tile in the short term. But tile replacement is always the best option for long-term durability.
Source: The Spruce