The digestion pool requires a particularly vile colour scheme to represent the bubbling biomass. Paint the whole piece of scenery Chaos Black and the edges an appropriate colour to match your gaming board. Then, using your large flat-headed brush, drybrush the pool with Dark Flesh.

Next, drybrush Graveyard Earth over the pool. You may need a couple of coats to make the colour stand out. Make sure that you leave a gap of Dark Flesh around the edge of the pool to give the impression of different depths.

Once you are happy with the Graveyard Earth, drybrush Dwarf Flesh over top to yield a nasty fleshy appearance to the terrain.

To make the bubbles look more disgusting, use a large drybrush to apply Scab Red around their bases.

Next, drybrush small patches of Liche Purple around the bubbles.

Drybrush small amounts of Blazing Orange over the rough areas of the pool.

To finish the painting, drybrush Golden Yellow over the Blazing Orange.

Finally, use Water Effects to create a wet appearance. Build up the pool with two or three thin layers. Make sure you use a soft brush to cover the surface of the bubbles.