Done it
here.
When you open the DDS file, you should have 4 layers, Alpha (the mask), R,G,B
I just copied the whole 'B' image into 'R' and blanked 'B' after that.
It effectively made Red the dominant colour.
Save the DDS file as a 32 bit DDS ( Alpha=8 bit, Red=8 bit, Green=8 bit, Blue=8 bit)
