Need to clarify...this beautiful white glass photo is NOT my backsplash, but it is what I expected mine to look like, except in 3x6 size. I am posting my "problem" below. The white ceramic tiles are there to provide color comparison.

The tile was a very nice colorless beautiful bright white before installation. Can someone tell me what went so terribly wrong?

A quick guess would be grey thinset instead of white. Glass tile has very specific setting requirements.

I agree. Most likely the thinset but could also be lighting, surrounding surface reflection, and/or the wall color before install.

I've been looking into glass tiles too. Apparently, there are different types of glass tiles, some that have the glass's normal blue/green tint removed. It is more expensive. But in your case, it's probably also the lack of refraction- when the tile is mounted you lose the light source from the sides of the tile and only see the flat side. So it looks very different loose than mounted. The big box white glass tile takes on a blue gray cast once mounted because that is in the glass. My guess is the tile in this picture is the "virgin" tile that has the color removed and is much more costly.