Additional troubleshooting steps:
* Make sure you save your changes in the Theme Customizer. The custom color will display as a preview as soon as you change it, but it isn’t published until you save your changes. This goes for all settings in the preview.
* Make sure Twenty Fourteen is the active theme when trying to change the colors – it currently may not work when live-previewing themes.
* If it isn’t working with your child theme, try activating Twenty Fourteen then visiting the theme customizer and customizing the colors. If that works, your “child theme” isn’t correctly identifying twentyfourteen
as the parent theme.
For additional assistance, please open a new thread for your specific issue with a link to your site. In most cases you are very likely to just be missing something in the setup or usage process, rather than there being an issue with the plugin itself.