Question: The border tiles in my master bath shower look horrible! The tiles are dark brown, but the colour is slowly coming off, probably because of chemicals in cleaning solutions. The tiles are not flat and smooth like the surrounding tiles. Is there any way to paint them?
Answer: Painting is probably your only option, short of replacing the tile.
Although it's possible to use standard paint to coat tile if you first scuff it up with sandpaper and apply an epoxy primer, manufacturers generally warn not to do this where the tiles will be frequently subjected to water, such as on walls around a bathtub or shower.
To coat tiles on shower walls, you need specialty paint. One example that's widely available is Rust-Oleum Tub & Tile paint (Find at Leroy Merlin or Build It in SA). This two-part acrylic epoxy comes in white and two off-white colours, Biscuit and Almond. The packaging warns against using it on surfaces exposed to "constant high humidity/water immersion such as swimming pools, hot tubs, ponds or saunas." So, assuming your shower isn't in constant use, the paint should stick.
Alternatives include Fired Earth Kitchens & Bathrooms and Dulux Bathroom Plus Sheen epoxy paints, which have the advantage of coming in numerous colours, including brown. You can order these from the company websites. If the surface, once prepped, isn't as smooth as you want the final finish to look, you'd also need the two-part primer, because you can sand the primer (once dry) to create a smoother base.
Follow package directions carefully; they differ by product. All of the paints, though, stick better to a surface that is scuffed up rather than slick. The instructions often say to scuff with sandpaper, but the texture of your trim tiles probably makes sanding impractical. Instead, use a wire brush or an abrasive cleanser and a heavy-duty scrub pad, the type that's often green and is designed for pots rather than non-stick surfaces. Rinse thoroughly and allow the surface to dry. Mix and apply the paint as the manufacturer recommends, being careful not to smear it onto grout lines. A brush about three-fourths of an inch or one inch wide would probably work best, but also have a small artist brush available for dabbing paint into recesses and whisking away drips.
Rust-Oleum warns that small bubbles may appear as its Tub & Tile paint is brushed on. If you use this product, don't keep brushing in an attempt to eliminate them. Too much brushing will keep a smooth coat from forming and isn't needed anyway, as the bubbles will go away on their own.
Once the project is done, wait the recommended time - probably several days - to use the shower. And switch to a cleaning regimen that avoids harsh chemicals. Using a towel to dry off the shower walls after each shower or series of showers is one way to prevent mildew and buildup of soap scum. A squeegee also works, but not on textured tile.