Probably "normal," for better or worse. We had a seized caliper on ours several years back and the shop replaced both with re-manufactured... They too ended up looking like that in no time. When it was time for the next brake job, here's what it looked like:
From what I understand, the OEM calipers have a coating that's supposed to prevent corrosion, but re-manufactured calipers may not have the coating. I really don't care for the looks of it, but allegedly the corrosion is "cosmetic."
The piston in the caliper pictured above would not compress when I went to replace the pads, so it was time for new calipers again. I replaced them with a pair of Centric Posi-Quiet loaded calipers which have a nice gold coating on them.
Before it gets too bad, you could probably clean up what rust has already formed and paint 'em.
03 Vibe base. Born 10/14/2002 06:07 AM
Neptune. Auto, Moon & Tunes, power package. 130k mi.
'13 Sonic LT - 1.4L ECOTEC turbo/6A. 90k mi.
'15 Escape SE - 1.6L EcoBoost, FWD. 43k mi. (hers)