weird lights sighted by brothers & only recalled years later.

One night in the late '70s my brother & i were staying at our grandparents' in swinton, near manchester. It was summer i think, certainly a clear night and not cold. In the early hours one night our gran woke us and said we should come and 'see something'. We followed her to her room, where our grandad was at the window looking out & up. He was looking at a bright light, or close collection of lights, which was stationary in the sky outside, at a guess about 2-300 feet up. No exact shape was discernable, only bright lights cycling through red, green, yellow & possibly blue or white. I clearly recall looking to my side at some point and seeing our grandparents and my brother lit by the coloured lights. My brother & i only began to recall this in our twenties(i'm now 35).We don't recall the duration or conclusion, sadly.
Date is approximate.  We have assigned an arbitrary date so that the report sorts in the database.  PD