Select tags and AJAX

Here’s my situation. I’ve got a select form that I’m populating with a
list of colors. I then have a database with a list of products, and each
product has a specific color. Some colors have multiple products (ie.
there are several “green” products). Based on what color the user
selects, I then want to display (below the form) a list of all products
that match that color. What I’d like to have happen is, rather than
clicking on one of the options and hitting submit, I’d like the page to
(via AJAX) update when I click one of the options. Does anyone have any
suggestions on how to do this? Thanks for the help!