Hi Rick,
You can't trust the colors on your computer screen. I guarantee you they look different on every monitor. Other than that, let's say they are close.

You should really find an actual grout chart, say for Custom grouts (Home Depot) and look at that. The TYW colors are scanned directly from the manufacturer's chart.
Another thing. With stain you can't make radical changes in the grout color you have. Our chemist says about 4 or 5 shades in either direction. The coverage is figured on the average grout joints within a square foot of floor. Coverage varies, of course.
Tile Your World Stone Armor is the best impregnating sealer on the market. I say this without exagerating. It is similar to Aquamix Sealer's Choice 15 Gold but it has a bit more viscosity (more solids). It will work well on your grout joints and on stone.
I'm going to move this thread to where our chemist, Tim Thomas, usually hangs out. We'll get his comments. Might not be until tomorrow.