The stonework is all carved DAS (see MRJ 260), colours used are mainly enamels in grey, light stone colours, brown, black and white. The green growth on the waterline is neat acrylic in green and yellow out of a tube. Also mixing Tamiya acrylics and Humbrol is not unheard of and produces some interesting effects! Nothing beats a bit of experimentation and if it doesn’t look right, work on it some more. It usually takes three or four ‘sessions’ to build up the depth of colour.