What I suggested works, and I prefer this because it is clear it is a number, and not a variable whose name happens to start with B.
It looks similar to 0x0F (where x is for heX), so 0b01011111 reminds you that the B is for Binary.
After all, B0 is a perfectly valid variable name (like X2 or Y3) so to have B0 really represent a binary number is a bit confusing.