I have had long hair, short hair (almost down to nothing) blue (and every other color) hair, a Mohawk (a real one, not a faux hawk) and dreads so I would be a hypocrite to not allow them to do that. It needs to be their own decision though and I would ask then to wait on the dreads and major color changes until 16 as the color is a lot of upkeep and they would need a job to pay for it and dreads are a bit of a commitment IMO so I would want them to be ready for it.
I am not fond of a mullet but whatever floats your boat ya know. It's just hair
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