New owner

Hello one and all. Just bought a 1990 Surf 2L.
Inside the rev-counter are two rectangular lights. One is green and seems to indicate when the turbo is boosting. What is the orange one? It seems to be coming on sometimes for no apparent reason and then going off again a few minutes later.
Also anyone (preferably UK) got an owners manual for this or similar model they would be prepared to photocopy or lend to me so that I can do it? I have bought the Haynes manual but some everyday instruction would be handy.
Many thanks in anticipation!
Richard