1. You first want to make the cloud/smoke effect in gray. Create a new 700 x 700 pixel file (or any size you want).
2. Fill the background layer with the light gray color sampled from the corner of your image.
3. Create a new layer and fill with 50% gray. Change blend mode to Overlay. Go to Filter>Noise>Add Noise. Set the noise amount to about 20%. Then blur this layer by approx. 2.5 pixels.
4. Create a new layer above that and sample the darker gray color of your cloud. Select a soft brush and set the Flow to about 20%. Slowly brush-in your cloud, making repeated passes with the brush as you move toward the center to gradually darken it in the center.
5. Change the blend mode of your cloud layer to Multiply (to allow the noise texture to show through). Reduce layer opacity to your taste.
6. Add a Solid Color Adjustment Layer above all other layers and change the blend mode to Color. Use the Solid Color adjustment layer to select any color you want.