Locomotive hauled passenger trains ran out of Bostonon the B&M until October 25, 1959 (on PAPER, actually it is believed that ONE additional loco hauled train to Portland ran for an additional week or so, but that's getting off topic).
I would agree with the above poster who stated that NO heavyweight coaches got painted in the blue colors. INTERESTINGLY, there is evidence that suggests that a very few prewar heavyweghts DID get repainted during the McGinnis bluebird era, HOWEVER they were repainted into the maroon colors.
This is NOT to say that such a bluebird scheme was not designed for these cars. Perhaps some long forgotten blueprints for such designs may surface sometime.
One thing that has been discovered recently was several UNUSED designs for bluebird schemes to be tried on the passenger diesels. These are basicly variations of the ones that were used and that we are familiar with.
Being the fan of the HERBER MATTER /McGINNIS color schemes that I am, several years ago, I speculated what a heavyweight coach might look like in the Bluebird scheme and applied it to an O gauge model.
The scheme was as such:
BLUE body below the widows, with B&M insignias next to the vestibules.
BLACK window band.
BLUE Letterboard above the roof, WHITE lettering.
BLACK roof.
Once again, this was purely speculative, but the thought of seeing a string of these coaches rolling out of North Station behind a blue E-7 warms the heart.