does Range Tinter work with alpha?
Just in case it doesn't, or if you want to retrofit Color Replace with alpha support
Premultiplied alpha means color rgb(0.8,0.8,0. with an opacity of 50% gets stored as rgba(0.4, 0.4, 0.4, 0.5).
To get the original color, just divide by the stored alpha!
color = rgb(0.4, 0.4, 0.4) / 0.5 = rgb(0.8,0.8,0.
then do your color replacing magickqs and then re-multiply by alpha.
*All vector notation here is faux and does not work at all like that in shader code.