I think in your case, the blue color results from the anchor-tag, which renders the whole passage as a link. Simply remove the anchor-tags. You don’t even need RegEx to do this, a normal Search and Replace should be sufficient.
Be aware, however, that I can only judge from this one example you provided. It is your responsibility to ensure that your other notes are of the same nature. Should some of them actually DO contain valid links, these will not work anymore after you remove the tags.
Backup your data first.
Open the Anki-Browser.
For starters, try it on one note only. Then on a small selection of notes. Proceed at your own risk!
Ctrl+Alt+F should bring up the Search and Replace dialog (Suchen und Ersetzen)
