Patrol earth with dead explorer ghost shell make sure you are doing patrol beacons though. Or Venus and go to citadel with a vex consumable. Ignore the hobgoblin area as just farm from the beginning of the bridge, the two minotours (sorry for spelling), the adds that lead to the other 3 minotours, loop back up to beginning of bridge and repeat. Guaranteed 3 yellows and usually a couple of extra. Only problem is taken screw it up.