Paper is a drawing application made by FiftyThree for the iPad, that has earned some attention. FastCompany has a story on what seems to be the central tool of Paper: The Magical Tech Behind Paper For iPad’s Color-Mixing Perfection.

The article follows the authors on their thought process, from the starting observation that linear interpolation in RGB space leads to unpleasing results, to experiments and eventually, the final tool.

(Illustration with the kind permission from Chris Dannen)