Everything covered but the four diamonds: the same gray.
Lighter or darker?
Adelson’s snake
Are the diamonds on the dark band lighter than those on the light band?
No: all four diamonds are the very same gray.
Why? The half-ovals make the picture look like a curved strip seen through a hazy glass. Your brain decides the diamonds behind the dark haze must be lighter than they look. Edward Adelson drew it.
Picture: Amaraldo.c, after Edward H. Adelson, CC BY-SA 4.0 · Wikipedia(opens in a new tab)