This is default behavior in your browser, which colors “visited” links differently from standard or active links to let you know you have clicked it before. You can disable this behavior or customize the default color in your browser settings. Please refer to your browser’s Help tab for detailed assistance with using its options panel.
You may set the color of visited links specifically for your website if you wish. This ensures they are the same color for all visitors that view your site. The following can go in the Custom CSS box in Theme Options:
a:visited{color: #888;}
Replace 888 with your desired color code. Note that some links need special class names in CSS to be affected. See the following for further help: