I agree that these characters are very distinctive in the manga. I got pretty lost in Ranma 1/2 because I muddled people up.

For the Hikago anime, I read that they'd chosen a color for each character and decided that the eyebrows would always be visible through the hair (unlike in the manga). It took me a while to get used to Akira having green hair - cracked me up the first time I saw episode 1. As for his haircut, it looks like one that a parent could do themselves, provided they could cut straight and the child held still...