If you look at a tube of artist quality watercolour, you will sometimes find some helpful information - usually pigment number and lightfast rating. If you look on the manufacturer's website you may also be able to find out if it is staining or easy to lift, transparent or opaque, or somewhere in between. I like to do my own tests - lightfast, lifting, staining and so on. Here's an idea of how to go about it. It's best to use the sort of paper you usually work on so you can see how each colour works for you. Want to know more about watercolour? I have put together an on-line introductory lesson and a series of classes called Mastering Watercolour that you can find on my website here.