“You’ve used keywords to search for images, but have you used color?
With Splash, you can now browse a subset of the 500px Marketplace by getting creative with color,” is the line offering the app 500px’s online service.

Users simply go to the webpage, select a color and spraypaint it or draw it onto a blank canvas, and the app finds similar pictures in real time — yes, real time. As you draw, the app will update its similar picture results.

500px website