Use the magnify tool to capture colors on the screen. To bring up the magnify panel press ⌘4.
Hover over the portion of the screen with the color or colors you want to capture.
Press control+option+command+L (⌃⌥⌘L) simultaneously to capture the portion of the screen.
When the magnify image is locked you can drag any of the colors to the main window palette to add the color. Locked colors displays up to 30 colors that are found in the locked magnify image.
Note:If you can't remember the key combination to capture the screen, just look at the menubar under Tools > Lock magnify image.