I'm not sure how you do it, i don't know if you can but if you didn't know then these might help you out...
(1) If you go on
http://www.thesims2.com and then at the top, put your cursor on exchange, but don't click. When You do this, what should come up is 'objects, sims, houses, stories.' (maybe not in that order) and click on Sims, you can download sims, and some of them will have different coloured or dyed hair. (you can do a search for just boys, just girls, only teens, etc. on the left of the page.) when you click on download and they have finished downloading, go to where you saved them, double click on them and say install when a box comes up. It takes literally about a second. If you already know this, then you could try...
(2) So if you want to do this, then you can go on
http://www.modthesims2.com and then go on 'live chat' (it should be on the top or down the left hand side), but you may have to register first, (registering is free) and ask people how to get Sim PE (WARNING! when you try this, it is POSSIBLE to get a VIRUS or mess up your computer, so it is at YOUR OWN RISK!!!) or anything else you need to ask, (if they don't answer you, copy the question you ask and paste it until they do answer you), and i hope that this has helped you!