An interesting way to monetise captcha. I'm not sure how hard it would be to break - they say they "pixelate the image differently each time".... seems to me you could fairly easily map average colour to phrase. e.g if the captcha is mostly yellow, the phrase is "browse safer". Calculating avg color isn't hard.
But supposing they do a hue rotate or something clever (and evade OCR scripts) it's an interesting idea.