The colors on the Mk I tanks was quite unusual . Go to www.landships.freeservers.com. Then click on On W.W.I Tanks and AFV;s and scroll down to the bottom of the page until you come to On Camouflague and markings and click on Camouflague of WWI AFVs. There is a fine article on the colors used by the British and this includes the Solomon J. Solomon scheme used on the Flers tanks of 1916.