Just had a look at your file. Gimp can read PSD's, but the blending modes revert to default when those modes aren't available in Gimp. Probably Color Dodge. But yeah, I could get the basic idea. Your work is pretty neat, compared to mine, actually. :P
You got the fractals pretty dead-on. Worked pretty well, but you shouldn't use the same fractal twice, even if it's a different colour. You overlayed red and blue to make purple, why not just make one purple one?