A couple of days ago, I saw this monk seal resting on the shore below Upolu Airport. It turned out to be RA20, the same seal I saw there back in May (bottom photo). In the interim, she had obviously molted and looked very shiny and clean. Pre-molt monks seals look quite ratty and green, particularly around the flippers and head. After a molt, they look sleek and silvery as this one does.
Monk seals molt about once a year and it is a process that can take 10 days or so. During this time the seal will generally remain on the beach or rocks where it has hauled out.