TIL That Oscar the Grouch is actually Orange

One question that comes up for me is why Oscar is green while his cousin Moishe Oofnik is brown.

The answer appears to be that Oscar is actually orange, as he appeared in the first season of Sesame Street in 1970. Only in Season 2 and later did he appear green, as explained:

Within the narrative of the show, Oscar explained his color change by claiming he went on summer vacation to a damp swamp resort called Swamp Mushy Muddy, where he became completely covered in slime and mold.