The smoke is gray. In Photoshop, I created a new layer and set the blending mode to color, then in that layer:
1) Selected some random area with the lasso
2) Feathered the selection so the color will fade at the edges instead of creating a hard line
3) Filled the selection with some color
How did you DO THAT!!!! I have always loved these artistic smoke shots! It seems to me like they win ribbons. This one seems like it should for sure :)