You can use the color selection tool to choose a color from your photos to set as your background color, stroke color, text color and more.
Color Selection for Mac (Mavericks)
To change your background color, click the Change Background Color tab and choose your background color.
Color Selection for Mac (Yosemite)
With the Yosemite update, Apple made some changes that affects how the color selection tool works in Fundy Designer. You can still use the color selection tool, however the eyedropper function no longer works.
The good news is that Apple has it's own color picking tool called Digital Color Meter.
Digital Color Meter
Digital Color Meter works in both Mavericks and Yosemite. The DigitalColor Meter is an application that comes installed with every Mac. Its primary use is to locate a color on your screen and provide the values of that color. Those colors can be provided as three different values such as RGB, Hexadecimal, and as a percentage.
You can find the DigitalColor Meter located within the Utilities folder of the Applications folder on your hard drive. Once open, you’ll notice that the app is quite simple.
Move your mouse around the screen and the Aperture shows you the color you are currently hovering over. To the right of the Aperture you can view the color swatch that you're hovering over along with its RGB values. Once you have chosen a color that you want, enter the RGB values into the RGB section of the Colors menu.