I just read, in a 2011 obituary, that it was Brian Moore who composed Hang Out Your Brightest Colours. The obit was written by John Gray, who participated in the ballad group "The People of No Property" along with Brian Moore, Dave Scott and Joe Mulhern. So he should know.
https://www.culturenorthernireland.org/article/3853/obituary-brian-moore-1946-2011