ColourMatch is a tool which lets you search 500px's photo library either with a single colour, or the colours extracted from a photo you choose to upload. The photos you upload are not private. You don't want to be the next Jennifer Lawrence. They may be displayed on the front page as a suggested search image for other users. For the sake of your own privacy, don't use any photos that you wouldn't feel comfortable putting on your Christmas card.
(Also, please be considerate to others! Don't use any photos which feature violence, nudity, narcotics, or Nickelback frontman Chad Kroeger's face. He scares me.)
This is the internet. There is no undo button once you release something into the series of tubes! However, I'm happy to do what I can to mitigate any potential disasters. Contact me via twitter or email and I'll happily delete any photos or data you'd like me to.