Would it be rude to ask my 16 year old if he wants to dye his hair?

My son is 16 and he has for the last 2 years been experiencing premature greying. He's been getting grey hair since he was 14. He's been some years in foster care because I went to jail and his dad was struggling with addiction. He was in foster care for 8 years and has been in therapy for years. I'm not sure if the stress he from foster care and or trauma he suffered from his foster parents that caused the greying but he's been getting a while now so it's noticable and his friends make fun of it. Would it be rude to suggest he dyed his hair

Edit: I'm not trying to bully him. He's been through a lot in his life which is why he's in therapy. Having greying hair at 16 I feel just adds to it. It's very noticable because he has brown hair but so much of it has gone grey/white. I'm just trying to help him feel confident

Edit: To Ki of course he has trauma from not being with me and his dad but I don't understand how I'm not allowed to be upset at his foster parents. They got paid to abuse my child. When you become a foster parent it's because you are supposed to want to help a family who can't take care of their kids right now. I know what I did wrong. His dad knows what he did wrong. I know that caused him trauma but a lot of it did come from the abuse some of his foster parents put him through and I'm confused as to why I can't be upset about that or they can't have any of the blame.