How to change my theme's link color

You’re looking to change the color of the links in the content are. You can do that with some custom CSS. Please try adding the following CSS code in the style.css file of your child theme or add it in your site using the following plugin:

https://www.ads-software.com/plugins/simple-custom-css

.entry-content a{
color: blue;
border-bottom: solid 2px blue;
}

Hope this helps ??
Best Regards
Poonam Namdev