I took Monday off work and, besides running a couple of errands, managed to make considerable progress on upgrading the old chipboard squares.
Firstly I mixed up industrial quantities of colours that approximate to those I use on my bases. I used a mixture of craft acrylics (from Hobbycraft) and cheap "student" artist's acrylics from my local bargain shop. These colours were applied in irregular splurges across the tables.
The effect at this point was reminiscent of an SS camouflage pattern but I didn't panic. I applied progressively paler layers of dry-brushing to bring out the texture of the surface and to blend the colours together somewhat.
Finally for day one I applied some patches of Woodland Scenics Blended Turf (Green Blend).
The next step will be to add patches of static grass in two different colours.