Blues = Patrol Dress = black-tie equivalent at least for armoured and sigs,I believe:
The pic is of A sigs captain PATROL UNDRESS. Dress blues are another category are a form of full dress number 1 ceremonials. Like the scarlet jacket in most other units. Unless grandfatered, in Canada only army reserve and Mil Col cadets wear patrol undress. Mess kit isncovered in the #2 dress. Things like facing and lace coloursusually translate from full dress ro mess dress. Ie PPCLI wear a scarlet jacket with French grey facings (cuffs and lapels). You will see grey lapels, cuffs in both #1B and 2.