Kevin has the right description of the aluminum sheets used by A/S. They originally used 24ST (2024T# clad) .032 gauge. Then for economics they switched to 3005 or 3005 sheet with H2 or H4 temper (1/4 or 1/2 hard), but because of the lower yield strength, they increased the gauge to .040". These grades of aluminum (3xxxx) were being used in the automotive trim fields and they had good appearances for exposed applications.
5052 is more of a marine grade or truck body grade, stronger than 3003 but not as strong as 2024-T3. If your 5052 sheet is .040 thick you are OK as far as strength goes.
I believe the difference in appearance you see is due to the age of the sheets. Your 5052 is newer and less oxidized vs. the other panels on your A/S. Over time, they should blend to be more uniform. If you have discolored clear coating on the old panels that will make "blending" more difficult. That would be the case whatever grade of aluminum you used.
The surface finish of sheets is important. Standard "mill finish" vs. "bright" finish will not match up without polishing the "Mill" finish to match.
Play with the finish on some 5052 scrap pcs and you may come up with a match. OR, let mother nature run her course!