The original Coloured airways were the first one's between LF/MF freq' facility,prior to the establishment of the VOR(late 50's early 60's)..Utilizing the medium waves the reception wasn't effected by line o;sight (as per VHF)ergo the MSA's were Lower(MOCA),but, as you know ,were effected by WX,sunsets,and ground metals ...the last few years they have been designated ICAO alphabet in place of colours.the present ben
eifits are that they show airways with much longer legs than VOR coverage..
