The scene right after the shark attacks in the pond, the kids swim to shore and the Chief's son is in shock. The Chief yanks a red blanket from the sand to cover the boy, but as he's covering him, it's an olive colored blanket.
uhhh... okay... since we watched the same movie, I wonder where the hell you got that "family blanket" thing from, since their blanket was not on the pond side. Besides it happens AS SOON AS he grabs the blanket, no time to realise his error, change it , bla bla bla.
oh come on! In a situation like that if he was rushing to his sons aid, I don't think he would be real concerned that he didn't grab his "family" blanket(I'm curious to know myself where in the world he came to that conclusion). He just grabbed whatever blanket was available and who cares what the owner thought. The family blanket, Geez...
When Chief Brody pulls up the red blanket, he runs towards another umbrella, not back to his son, we have to assume that as he bends down before the scene is cut, he picks up another blanket (the olive and blue one). In the next scene they lay Michael down (presumedly on the red blanket) and cover him with the olive and blue one.