I wonder if I can convert it? I saved it both as a PNG and also as a FPA file (the Flame Painter format), so I think I can import it and still have the layers. Yes, that worked. However, I'm not sure how to change the blue into orange/red. I can easily change it into black, just by removing that layer (actually, there were three of them):
Then I added layers (keeping the blue ones invisible) matching those three (in terms of the Z-depth), painting with a red/orange flame:
Neat, enjoy! :)
:D