Ah. - just spotted that the formatting of my little table gets all screwed when posted here :-( - but you can get the jist of it I hope ! Tests 1,2 & 3 were in the light, test 4 in the dark. and e.g. on the first pair of lights 'Red2 and White' I identified the Red correctly and the White as Green in all 4 tests. Kev.