Number - Proportion of the original red colour to remain, from 0 to 1
green
Number - Proportion of the original green colour to remain, from 0 to 1
blue
Number - Proportion of the original blue colour to remain, from 0 to 1
alpha
Number - Proportion of the original opaqueness to remain, from 0 to 1
Notes[]
These values only modify the existing colour and alpha of the backdrop files; it its not possible to be lighter or more opaque than the original
Subsequent calls to the same function will override previous ones; i.e. they apply to the original texture directly rather than interacting with the previously-tinted one