Everyone by now knows about CAPTCHA - Completely Automated Turing test to tell Computers and Humans Apart. Almost everyone has their own CAPTCHA, and they all look the same: bland gray images with distorted barely-legible letters.
Since the elder days of Hotmail, CAPTCHA images have looked mostly the same, with very few exceptions to this rule. As for myself, I've experimented with the user of color in my CAPTCHA based off of some challenging 'Ishihara tests' I found on the web. I don't know what the tests are for; I wasn't really reading the page so much as looking at the pictures. In any event, try out my CAPTCHA—test your humanity!