@shonen: I wasn't talking about Vegeta's first appearance where they messed his entire colour palette up. Vegeta has dark brown hair, it's much more noticeable in the original Japanese broadcast of Dragon Ball Z and maybe the Dragon Box releases that stay as close to the original film as possible, but it looks completely black in other releases of Dragon Ball Z because the colours are darkened. The difference is much easier to see in newer Dragon Ball Z material too, take this screen cap, for example.
If King Vegeta's hair colour was wrong, I imagine they would have changed it after his first appearance like they did with Vegeta, but they didn't.
I checked the ages on the Dragon Ball Wiki. Goku was introduced as a 12 year old and was 15 by the King Piccolo saga, Krillin is a year older. They were both short and both grew somewhat since they were introduced. The only difference between them is that Krillin continued to grow at the same rate, while Goku had more of a growth spurt over the next three years (pretty normal when you consider it's three years worth of growth). Rate of growth aside, the point is Goku and Krillin are both more or less fully grown by then, Goku is 18 at that point and Krillin is 19, generally about the time a human is fully grown. Therefore, Goku didn't have a "lengthy adolescence" at all.