You'd be lucky to get one larger than 4' in blue. Proven Winners' Let's Dance Rhapsody Blue is brand new and puts out a deep blue rivaling that of older ones like Enziandom, but supposedly gets no larger than 3'. Here's my new one from nursery stock, planted in acidic soil:

Paniculatas can't change to blue, but ones like Grandiflora can grow into 25' trees.

IME you can choose large or you can choose blue this far north. My H. macrophyllas (the ones that can turn blue) die back to the ground or the snow line each winter and then resprout and bloom on new wood each growing season. They don't get larger than 4' high. My Endless Summer is a nice medium clear blue and blooms all summer.

My H. paniculatas are hardier and keep their old wood and are over my head at perhaps 7'. They start pale green, turn white, and then end the season deep pink.