What would you do in this instance?

I would speak to the teacher and she can watch for this behaviour and address it as he/she won't tolerate this but may also be completely unaware (I work in a school).
Bullying, especially in yr 1 is just so sad. I would advise your child to seek support from staff too when it happens so he doesn't have to sit on that all day while he waits for your comfort

I’d personally say ignore it for now and see if anything else is said. It could just be a one off. I’d also try keep reiterating to your son that other peoples opinions don’t matter and as long as he likes his hair then it shouldn’t matter

It depends. I would ignore it unless it continued or if it made my child not want to go to school. A girl told my daughter she was ugly during transition day. I normally tell my daughter to play with her own friends and focus on them.

I would let a one time mean comment go. Tell your son that if he likes his hair, that’s all that matters

I would teach him to speak for himself - I watch that lady who supports kids who are bullied and she explained that the importance of advocating for oneself by using role play. Ask him what he would like to say to the boy- explore with him different options- maybe ask him if there is some friends he can stay with so he can get away from the boy. It is good that he told you what happened he just want help to navigate the situation

Bring it to the teacher/admins attention and tell them you aren't trying to make a big deal about it but also want it to be on their radar so it doesnt escalate into something bigger. And that you will follow up with them about it in the future...Being proactive can help eveyone out. Teachers dont always see these dynamics until they escalate.