Saw your other post on the PolyBlend Snow White, "is it yellow?" thread. Haven't tried Polyblend's "Snow White." It may in fact be white. But I do know that all of Polyblend's "grays" are biased-warm in hue (they have some yellow in them), no matter what their printed color chart leads you to believe. We first grouted our entire floor in Polyblend's "Delorean Gray," and next to our neutral-gray tiles, the grout looked brownish-beige. In fact, the grout just appeared dirty next to those tiles.

So, we switched to a Hydroment-brand grout, specifically because their grays are slightly bluish to neutral-gray in hue. We chose Hydorment's "Blue Heron," which was the closest match to our neutral-gray tiles. It has very slight bluish hue, but appears very close to a true neutral gray. Hydroment also makes a lighter shade called, "Ice Blue," that is a very light gray, almost white. In our application, Heron Blue dried a shade lighter than the sample chip, but we hope that an application of a Miracle 511 sealer will darken it a shade. A tiler in another thread mentioned that the final, cured grout color is typically similar to the hue and lightness of the dry grout powder in the bag.

I would suggest you visit a Hydroment dealer and take some sample chips home. Hydroment's chips are pretty good--they're three-inch, plastic chips that resemble a short grout line. But, my best advice would be to buy a bag of each color candidate you may have in mind, and actually mix and grout something, let dry, then compare, in daylight, your tile next to the grout color when dried. It's the only way to really tell. But, realize that, if your tile is pure white, any grout color of any measurable difference in hue or lightness will tend to create a grid-effect. Again, try it out on a test layout of a couple of tiles to make sure.

A personal aside on the subject of color selection in the home decorating world:

Since I have some experience in four-color, pre-press (prepping files for full-color print advertising), I find it extremely frustrating to find manufacturer's actual formulas absent from any swatches or labeling. I once asked for Baer's "blackest black" paint. Chose it from the blackest swatch they had, which of course, had zero technical data printed on it. It had yellow in it, because when the formula sticker printed out (after he had mixed it), it had a numeric value under the letter 'Y.' When I informed the paint-counter guy of this, he said, "How did you know that?"

I had to argue with the guy for 10 minutes to mix a pure black without paying for the "yellow-black." I wish I could just walk into a paint store and ask for a PMS300, uncoated, and get exactly that, a "USA Today" blue, a.k.a., "PMS300." Anyway, the point is, you often have no color data on any of this stuff. The only way to be sure is to buy some product, apply it, and compare it with your other materials, preferably under 5,600- to 6,500-degrees, Kelvin, daylight (e.g., a sunny day). Good luck!