如果帖子已被读取wordpress，则更改链接颜色

I want to implement a function to change the color of the link if a post has been read in wordpress no matter it is Visitor or registered user. I tried some plugin, but they are different from my expectation.

I really appreciate your help!

You can achieve this by using raw CSS, i.e:

    a:visited {
        color: red;
    }

After the link is clicked the color will be set to red.