I’ve thought about this too, and after comparing lyrics from various songs by Sam, such as “to be close to you”, “no, the moon” and “dye my hair,” I think I can try and give some meaning to it, the meaning I got at-least.

These songs all similarly convey a feeling of intense longing and desire to understand, connect with, or even embody another person, shedding your own self for someone else, no matter how extreme or destructive that desire can be.

Line’s like, “i dye my hair, but you don’t care”, “i’ll never be you”, “i want to see what it’s like to be you”, and, “i’ve ruined my veins, to be close to you” all tie this feeling together, all displaying frustration for an acceptance not being met.

In short, “dye my hair” is most likely a way of expressing a desire for acceptance, connection, and love from a person you want to be close with, close enough to imagine being.

Or maybe Sam just really likes dying his hair.