Boeing 757/767 Flight Crew Training Manual states on page 4.5 (Revision No 5 dated Oct 2005) that max RATE climb speed is Flaps up Manoeuvre Speed + 50 kts. This equates to Vref30 + 130. Forgive my ignorance as I did my theory exams a while ago, but if Vy is the same as Max Rate Climb speed, that's your reference.
If on the other hand Vy is max ANGLE climb speed- that is obtained from the FMC on the Climb page and will equate to roughly Vref 30 + 80 up to FL200, Vref30 + 100 to FL330 and then Min MN.
