I used to have dozens of reptile pets but now have none. Watching them live their lives was fascinating and entertaining to me, and I miss it.
So watching the turkish geckos who live on our patio (and front porch) is something I enjoy on many evenings, and have even moved the light so their antics can be seen from our couch.
I have discovered that just like a cat they will chase a laser's red dot up and down the walls endlessly, snapping at it as if the red dot is a tasty insect dinner.
On this particular night the one in the center caught a large moth attracted by the light (that's why they hang around porch lights) and within seconds the other two came running, trying to steal a meal.
Failing that, they would nip at the winner's tail. I don't know if they did that because these geckos twitch their tails when hunting--causing a natural predatory response--or if they are just little pricks to each other sometimes.
Fighting for territory is normal, so maybe that's what was going on.
The color variation seen here is normal, and is caused by a variety of factors.
Many reptiles will darken to absorb more heat from the sun, then lighten as they reach optimum operational temperatures.
Being mostly nocturnal, the turkish gecko may be using color as camoflage since the ones closest to the light are usually the lightest in color--to blend into the wall better--or it may be about temperature after all.