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If you have a black flame it's easy to recolor, you make the particle the color you want and invert it (The color that is).
I.e. If you want a green flame, you make the particle texture green, and then invert the color.
Gimp: Color>Invert
Photoshop: Image>Adjustments>Invert, will invert the highlight-midtone-shadow
If you have a different colored flame to begin with, things might get a little more difficult.
Last edited by Fenris; Apr 23, 2012 at 05:50 PM.