they were fitted to most bombers and fighters built in the latter part of WW2 they were on most early Meteor and Vampires plus Lancs and Halifaxes but ceased to be fitted after that time on new airplanes
The Puma HC1 which entered service in 1971 had blue formation lights fitted. One on top of each sponson and one on the doghouse. Flying formation at night with just the blue lights wasn't the most comforting of occupations but improved with NGVs as you could look down the exhaust shroud and see the power turbine lit up.
I don't know if they still have them. I hope not, it was ruddy dangerous.