Why? If it's harmful gibberish, the organism with that mutation won't survive. If it's neutral gibberish, it might or might not, but who cares? When that organism mates with one of the more numerous of its species that don't have the mutation, the offspring might get the original version rather than the mutated copy.
But then there's the case where the gibberish is actually a useful new word. In last night's Cosmos, they used the example of an arctic bear that had the mutation for white fur. This is obviously not that rare a mutation--white tigers are born on occasion. Where tigers live, white fur would be a disadvantage; but where arctic bears live, it would be very useful. So the white bear is a more successful hunter, lives longer, mates more often. Some of its offspring have the brown fur of its other parent, but some have the white fur because the new word gets copied. The white ones are more successful, mate more often, etc. etc. and presto: polar bears, a new species.
I don’t know if hair color is the greatest example. That would seem to be a case of turning off an existing gene for the pigment.
How did the gene sequence that causes hair to grow get their in the first place? Presumably there was a hairless creature that had the DNA necessary to produce hair, but it wasn’t turned on. Through a mutation, it gets turned on and hair turns out to be useful.
How did evolution know that hair would one day be required so the genes could be turned on? How many generations of creature had to carry this genetic code intact so it could be activated?