Gets or sets the gamma ramp for the display that owns a given window.
Note that the data for the gamma ramp - the V3 (Vector Word16) - must contain 256 element arrays. This triple is a set of translation vectors for each of the 16-bit red, green and blue channels.
This StateVar can be modified using $= and the current value retrieved with get.
Despite the name and signature, this method retrieves the gamma ramp of the entire display, not an individual window. A window is considered to be owned by the display that contains the window's center pixel.