"read more" open in new tab,new page or colorbox

I am running this site which automaticly takes rss feeds from other athletic greek sites , and convert them in to posts.
https://www.olympiakoscafe.gr/

When you click on the title or in the “read more” , it sends you to the source article of the source site.

That’s exactly what I want , but I want to open the source article in a new tab, a new page (via the famous JS script) , or even better in as colorbox… Automaticly of course…

I tried with entering <base target=”_blank”> just before the_content() in my index , but that makes my pages too in the page bar and everything else open in new tabs!!! I just want “read more” and the post title….

Any Suggestions?