Acid stains consist of earth tones. You may want to look at water-based stains/dyes instead. We just posted an article about a couple that did their basement with water-based stains and a matte sealer.
allgaragefloors.com
This. I've even done a white.
Yes, the surface should be lightly etched or sanded if water sits on the surface. Just know that etching can't be controlled. Color tones can get splotchy and areas become more porous than others due to the varying density at the surface. This is fine if you want a floor with a lot of character when you apply the stain. Sanding the surface would be better if you want something more subdued. Don't go too crazy on the grit though or you will have swirl marks. If you sand, make sure to do some water drop tests to verify that it's effective.
