Some of the original paint trials were carried out by C Sqn. The LIfe Guards in Combermere Barracks, Windsor. They were a Ferret only Sqn at that time and each troop was tasked with painting its vehicles different colors with provided paint.
Yellows, Greens, Browns, Blues, Sand, Tan etc. and the present Black and Green were all in the trials and the powers that be along with the Trials and Development teams chose the final product, and yes cost of paint was a major factor!
As for the urban three color scheme, it was well known by both sides of the wall how many of each vehicles were allowed to be stationed in what we knew as the Berlin Brigade and the paint scheme although very effective was not much more than a showcase item.
Keith.