Some good tips posted so all I am going to say it that you should keep it simple and that colour washes are the place to start.
A lot of people get caught up in trying to do a "wow factor" show when they first start out. I know that I did and it
bit me! Simple colour changes are nice and effective and will provide a great basis on which to
build future shows.
One think that I would strongly recommend is to talk to the performers and add notes to their
set list. For example, which songs are slow, fast, happy, sad
etc. This will help you pic which of your colours you will predominately use for that song.
Hope this helps.