explain the incident with Brathwaite's blood chapter 14

E.R. Braithwaite is helping the boys lace up a soccer ball. Braithwaite and some of the boys inflate the ball while a couple of others hold it down. As Braithwaite threads the lace through the last eyelet hole the steel lacer—an instrument for lacing up an old-fashioned soccer ball—suddenly slips and makes a small cut on his finger, drawing blood. This provokes an astonished reaction from Potter, one of the boys in the class:

Blimey, red blood!

Potter seems amazed that a black man has the same color blood as him. But in a sign of Braithwaite's growing acceptance among the children, Potter's classmates round on him, making him feel like a complete idiot for his less than astute observation. Yet Potter soon realizes the error of his ways, and makes another observation, this time one infinitely more sensible and perceptive:

I didn't mean anything, Sir; what I meant was, your colour is only skin deep, Sir.

Potter has learned a valuable lesson. Underneath the skin, we're all the same; we all bleed the same blood.