What is the bley (blay) color?
Around 2004 (if I remember correctly) LEGO changed the grey and dark grey colors. The colors before the change were the original grey colors which were in use from their introduction. They were somewhat warmer than the colors today, which was perceived as looking faded, though it had nothing to do with aging. Part of the problem was that the competition (Megabloks) was using more blueish greys, which made the LEGO greys look old.

The newer colors have a colder, blueish tone, and were widely disliked in the AFOL community, because most of the time they look awful if used together with the existing old grey pieces. Depending on the lighting it can also be quite hard to tell old and new greys apart.

Hence the term "bley" is used as a name for the new blueish grey.

 BrickShelf