According to this;
http://www.railuk.info/diesel/livery_search.php
Which seems to be a very comprehensive livery list, there is only one BR green colour listed;
"Green - B.R. Style"
http://www.railuk.info/diesel/getliv...=133&type=loco
I think it's based off Brunswick green, I am sure the shade did change over time and probably slightly with different depots, regions, etc. most likely for various reasons but I dont think there was a planned difference. There are of course livery variations such as with the Deltics etc.