..you could try some of those really cheap/party extensions first and see which colours suit your complexion and your style/clothes etc..if you still can't decide then why not go for something like this with a few colours../sorry it's not a great pic but most I could find were darker hair, rather than blonde but it's a great look I think...
..I'll see if I can find some more pics later and maybe you can see if you can get any inspiration from them...