It's easy - I just look in the MLS! Listing agents are supposed to disclose if a home is in foreclosure. Usually, they are short sales. Homes that have already been foreclosed on are called bank owned or lender owned. (Sorry if I'm telling you more than you need to know.)
Colorado has recently enacted new laws regarding making offers on homes in foreclosure, especially if you're an investor. Feel free to call or email if you'd like to know more.