Monday, 4 November 2013
An internet search into reasons for the colours produced this from Wikipedia, "The habitat defines its color. On sheltered shores it has a lighter and uniform color (yellow, brown, orange or olive green). On exposed shores its color is darker and chequered." ARKIVE seems to agree, "The colour is variable depending on the habitat. It is usually olive-green but may be brown, yellow, banded or have a criss-cross pattern. Lighter colours are associated with sheltered shores."
While the colour range was considerable, the patterns were also highly variable. Some had stripes running across the shell, a few had them running down the shell. We didn't find any that we could call 'chequered'.