We see some pretty unique grey leathers that are complex color blends.
The more blue that's in your grey, the more likely it is to wash out over time with exposure revealing the other tints in the dye. (explanation in the Linea Pelle Care thread where turquoise was losing blue; we also encountered Hayden Harnett's Eucalyptus that was getting greenish - losing it's blue- over in HH sf.) Some serious research and discussion with experts in the field helped me better understand this problem. I already knew blue to be unstable, but was determined to discover a means of preservation of delicate color. What we use to cleanse and treat our bags affects the color, too, so it's important to use the right stuff, dust covers, and common sense.
Leelee is on the right track. Unfinished leather, lacking a topcoat, is more vulnerable but there are safe ways to protect without altering soft matte qualities.
hth
