be An alternative for older browser could be to use mask produced by pseudo-elements or inline tags.
Absolute positionning hover an img (or text area wich needs no click nor selection) can closely mimic effects of color scale , via rgba() or translucide png .
It will not give one single color scale, but will shades color out of range.
test on code pen with 10 different colors via pseudo-element, last is gray . http://codepen.io/gcyrillus/pen/nqpDd (reload to switch to another image)