Striation

Striation (stripiness/streakiness), in Instarrians, refers specifically to the condition of having striped hair.

This is considered a sign of low class and a serious beauty fault.

Striation is natural and lifelong. It can be inherited (it's affected by more than one gene, though, and at least one is recessive, so this isn't entirely straightforward).

Stripes generally show up a few weeks after birth. The scalp itself is not striped. The pattern of striping, but not the presence of stripes in the first place, can change if the hair is shaved and grows back.

Women of a certain age (three or thereabouts) may develop striation in their hair, even if none was visible before. This, as a beauty fault and a sign of ageing, is obviously considered extremely embarrassing.

Certain hair shades (generally any colour without much yellow in it) naturally disguise striation, but the stripes could still show up if the hair is dyed.

Here's a striated redhead. With long hair like hers, the exact pattern of the stripes isn't too noticeable.