The upper hull of the Fire Prism was painted using this method; the light green is  "putrid green" and the darker green is "emerald green" (all the paint names are from the Citadel range of hobby paints) the different shades of green are achieved by applying a few layers of "orc flesh" wash.

I start off with the putrid green as a base colour and then paint the circular patterns on with the emerald green. I then coat the lot with Citadel's "orc flesh" wash (dark green ink).  The orc flesh wash darkens everything so I paint with the same two coloured paints again, making the pattern a bit smaller, so the total effect looks like 4 or 5 shades of green.

The highlights were painted using "putrid green" with some "bad moon yellow" mixed in to lighten it.

The prism (on the weapon) was painted light blue ("enchanted blue" mixed with some "skull white") first and then some darker blue thin stripes were painted on in a lattice pattern. 

The next step was to cover the prism with a blue wash (Citadel blue ink).  When the wash was dry, another series of light blue stripes in the lattice pattern were painted on.  After that, another wash was applied and then another series of stripes were added.