Ceramic floor tiles come in many colors, including colors you don't like. If you've inherited some dark, depressing shade of tile floor, and the tiles are in such good shape that it makes no sense to rip them out, it is possible to paint them a lighter color. It's a difficult surface to paint, requiring you to dull the previous glaze and seal it with polyurethane, but the result can be a tile color you can live with.
Go over the surface of the tiles with a vibrating sander and aluminum oxide sandpaper. Run the sander repeatedly over the surface until it's dull and free of shine. Go over it with tack cloths to take up the dust.
Apply a coat of sealing primer over the tiles with a paintbrush, spreading it on in a thin, light coat. Keep the brush strokes going all in one direction. Don't paint the grout lines but keep it on the tile face. Let it dry for 24 hours.
Apply the first coat of light paint to the tiles in the same manner, in a light, thin coat, keeping it off the grout lines. Let it dry 12 hours.
Apply two to four more coats of paint, as desired, keeping each coat thin and flat and letting it dry 12 hours between coats.
Brush on a coat of polyurethane gloss, again keeping the coat thin and flat. Let it set 12 hours.
Hand-sand the dried polyurethane with extra fine regular sandpaper. Sand in light, short strokes, dulling the surface. Use tack cloths to take up the dust.
Apply a second coat of polyurethane in the same manner as the first coat. Let it dry for 12 hours. Hand-sand. Wipe up the dust.
Brush on a third layer of polyurethane. Let it set for 24 hours.