>>402500747
>I suck at instructions
Looks about right ( alpha to red, blue pure white ).
In photoshop, select layer -> layer menu -> layer mask -> From transparency. This will extract the alpha to a layer mask.
In the Channels tab, enable only the newly create mask layer and select all, copy, and paste it into the red channel, then delete the layer mask.
Select the blue channel ( ensure others disabled ) and paint it pure white, and you should be done.
Sorry, no idea how to do it in Gimp. 
Probably simple with a Python ImageMagick/Opencv script