Should both of my garage door sensors be green?

No, both of your garage door sensors should not both be green, as they are designed to show different colors to indicate power and alignment status on most systems including LiftMaster, Chamberlain, and Craftsman. Typically, the sending sensor, which has a yellow or amber LED, should show a steady yellow or amber light indicating it is sending the infrared beam. The receiving sensor should show a steady green light indicating it is receiving the beam and is aligned. If both are green, it may indicate you have a newer model where both show green when aligned, but most common residential openers use amber and green combination. If one sensor has no light, it indicates no power, loose wiring, or failed sensor. If green light is flashing, it indicates misalignment or obstruction blocking beam. Both sensors need steady lights, one amber and one green, to allow door to close. If both are off, check outlet power and wiring connections at opener motor unit. If both are green but door still won't close, check for flashing which indicates misalignment. Keep sensors clean, ensure they are mounted 4 to 6 inches off floor, and keep gutters above garage clean to prevent water damage that can affect wiring. If lights flicker, tighten brackets.