I have some icons in PNG format which are basically green (with some grey shadows). Unfortunately, I need them in red!
Sample:

The icons all have graduated fills and have a transparent background. I'm banging my head against the wall trying to figure out the appropriate way to do this. A lot of the methods I have found result in a black background (instead of transparent) or mess up the shading.
Can anyone offer me advice on how to achieve this?
TIA
ImageMagick-6.9.2-3-Q16-x64