I've read this sentence on a story:
The neon lights and the white sheen off the walls make his eyes look bluer.
Why is "off" used here? Why not "...sheen of the wall..." Would it also work?
In this context "off" refers to the reflection of light off the wall.
It's not quite correct, since walls should have a sheen and not reflect a sheen -- the sheen is a quality of the wall's surface. But this writer might not have thought it through, and anyway it's not that big of a deal.
Similar examples:
The children bounced the ball off the side of the building until the owner made them stop.
I could see her, walking by the cafe, in the reflection off the store window