Beginning image:

1) layer--->new adjustment layer-->color balance and pick any colour you want

2) Now go to filter--->render--->clouds and press control and f until you see somthing you like

3) Layer--->new adjustment layer--->color balance and again pick a colour but make sure it is different to your first

4) Repeat steps 2 and 3 as many times as you want

5) If you want you can continue this but the maximum I go to is three times