How do you clean a composite deck?

I have a composite deck built last year, some leafs and residue were on it for most of the winter, and part of it has some green-brown color. I haven't tried to clean it yet, what can I use to clean it that won't damage it but will also remove any stains? If you'll say 'soap', please specify which kind, last year I tried dishwasher soap and it left white spots which were a pain to clean.