Valid sources say it used to be blue. Now the color of a deadman's face and thin with wear, it greatly resembles used, strung together cotton balls.Two things. One>> I suggest you make the period after "blue" into "but". Two>> "Deadman's" should be "dead man's".
He sits in honors Calculus, an average teenager or better, very adult and composed.I think the comma after "better" should be a colon or semi-colon.
Occasionally, thin ragged pieces anxiously unravel and detach themselves from their home.Comma after "thin".