What causes hair colour change?

[Illyrius]

You have seen my pictures now that I have dark hair.
Contrary to this as a kid I had blond hair
Around the age of 6 my hair started to darken rapidly.
What caused this.
How can I get back my beautiful hair.

[mitalit]

How can I get back my beautiful hair.

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[Insuperable]

Illyrius 30 years from now:

What causes hair to fall out? How can I get back my beautiful hair?

[The Blade]

What's wrong with brown/dark hair?

[Ford]

The melanin chose you to be poppin

[The Blade]

It's pretty normal. A shitload of blond children turn brown to dark-haired.

[Illyrius]

What's wrong with brown/dark hair?

Brown hair is fine but black hair not so much

[TheMaestro]

Wog genes kick in.

[PaleoEuropean]

You have seen my pictures now that I have dark hair.
Contrary to this as a kid I had blond hair
Around the age of 6 my hair started to darken rapidly.
What caused this.
How can I get back my beautiful hair.

You produce more melanin as you get older generally.