we have a 15+ year old concrete (shaped like a wave) tiled roof. in case it matters,
the original tiles came from a small manufacturing company in lake wales, FL and they
have/had an acrylic clear coating on top of a multi-colored surface.

I'd like to ask for comments on how to proceed to recoat the tiles, my own preference
being some type of stain that would make them all unicolor.

the roof has been regularly cleaned, pressure washed about every 2-3 years and the
tiles are in excellent condition but have faded into a single color plus there is a
fair amount of sandy colored residue that starts to come off the surface when washed

have not used any chemicals (ie. bleach) and have always washed with the pressure
washer on the lowest pressure settings, just enough to get mold and fungus off after
the rainy season

are there differences in quality or types of stains to use? brand names to look into?
what about the equipment - rent it or buy a sprayer? how about ongoing maintenance
after applying the stain?