Dust explosion question

[grit]

I would like to make this:


Now, explosion I would make with line nova,
but I don't know how would I make dust and
I don't know how to make non-uniform distribution of colors.

[Ofnuts]

Dust and non uniform distribution of colors call for randomness and the two best source of randomness in Gimp are FIlters>Render>Clouds>Plasma and Filters>Render>Clouds>Solid noise.

For the non-uniform colors, generate a plasma layer above you color layer, set it to grain-extract or grain-merge, and reduce its opacity to around 10%

For dust particles, use Solid Noise with X and Y size to the right ((small grain), then increase brightness and trigger to around 253.