College colours of the RNCM were a big political deal during the merger in the 1960s-1970s. The Royal Manchester College of Music had light blue, the Northern School of Music had dark green. The new college HAD TO have a neutral colour so that unconscious association wouldn't be inherited from either founder. Maybe a nice purple to reflect the forthcoming new royal college? (I mean, the RNCM is back to a sort of cornflower blue and gold so no one tell Ida Carroll if you meet her in the afterlife...)
Part of the #NSM2020 project "A 20/20 Legacy: the centenary of the Northern School of Music" supported by the National Lottery Heritage Fund.