How can I enter RGB or Hex color values for backgrounds in Interface Builder? I can select predefined colors but I would like to manually enter in RGB values. Where can I do this?
Click on the color slider icon, and then choose "RGB Sliders" from the drop-down list.
You can also use the magnifying-glass as a color picker to pick up an exact color from anywhere on the screen; also see @ken's excellent comment below clarifying how colorspaces work with the magnifying glass.