Everything gets old. Some things turn gray as they age.
Like this AC compressor. Poor thing. Getting old and gray, leaning a bit. It will only get older as the summer gets hotter.
Actually this AC unit is only 4 years old. Sure, it shouldn't lean, but that is an installation problem and an easy fix.
But why so gray?
Look under the gray box on the wall. The white trapezoid near the ground is the dryer discharge vent. The dryer is about 4' below that cover, just inside that wall.
THIS DISCHARGE IS TOO CLOSE TO THE AC COMPRESSOR! Why?
Air is drawn in through the fins to cool and discharge heat from the house a bit before the gas gets compressed and super cooled. The fins are gray, but with dryer lint. Notice how on the right side of the compressor the fins look a bit darker? That is opposite the dryer discharge opening. Less lint gets drawn in over there! Up close you can actually see little puffs of lint. But the "gray" color is actually a fine layer of lint all over the fins.
An AC compressor really should be about 12' from a dryer discharge opening. That minimizes its opportunity to draw in lint and get clogged. The compressor here is stressed, to say the least. That will not only affect the efficiency of its ability to cool the house, but also make it age faster.
My recommendation: When you look at a house, check to see if the dryer vent is blowing too near the AC unit. If so, make a note! It may be an issue that comes up later!