Are the señors misaligned if one garage door señor is green and the other one yellow? Should I replace the yellow one?

Have you aligned the sensors. That would be the first step. Be sure nothing is blocking either sensor. Check sensor wiring at the closer and the sensors. Apparently it will not closed because it is sensing something in the way of the door down travel.

Those things can be pretty finicky. Make sure there is nothing on the sensor lens. If you have room you could try putting them directly in front of each other.

They may also need slight adjusting, mine messed up after installation and I just had to move one up slightly.

Good luck.