If you're a photographer, designer or really any type of artist working extensively with color, the Croma app by Numix might be a very useful tool. It's a fairly straightforward app that allows you to create, save and share color palettes.
It offers three main ways to create a color palette. Firstly you can do it manually. You give the palette a name then Croma provides an extensive color picker to select the color you want to include, up to a maximum of four in the basic version of the app. The second method is for Croma to generate a palette from a single chosen color. You choose the color, then Croma provides a range of palette options relating to that color, such as Complementary, Clash and Tetradic. The third option, and the most interesting to experiment with as a casual user, is the ability to generate a color palette from an existing image. You choose or photograph the image from any gallery or camera app, then Croma generates a palette of the colors that feature most strongly in the image. This also means you can grab the color information from an email for example, if you need to know which color font was used.
For each palette, Croma displays the HEX values for each color within it. Tapping on one of those colors then shows further information for that color, such as the RGB and CMYK values. You can copy any of the codes to your clipboard and each palette can also be shared to another app, so you can easily send it to a friend or colleague. Of potential interest to developers, Numix have also shared the source code for Croma in Github as an open source project. The basic version is free, with a Pro version also available for just over $2 that allows you to include more than four colors in a palette, generate more palettes from one color and combine palettes. It's well designed and easy to use. If you work a lot with color or even just need some ideas on what color combinations might work most effectively, Croma is well worth a try.