Though I'm not positive, I believe it is likely an issue with your graphics card. I'm being hit with a very similar issue, although I am only getting the blue lines and not the yellow, although I have read about the yellow lines in researching my problem. I'm also getting dollar signs when booting up, and my PC can only pick up a default monitor. After doing a bit of research last weekend over all of those symptoms, I found out that those lines are usually due to the graphics card starting to fail. Although if you are only getting these lines in XIV, it may be a different issue. I'm not even able to log into XIV right now due to my specific issue.

The solutions that I have read about range from making sure your PC tower is clean on the inside, to having to buy a new graphics card altogether. I'm not necessarily a PC expert, I had to review articles on Google and watch some example videos on YouTube to diagnose my problem, so a more experienced PC gamer may be able to give you a more precise diagnosis and solution.

Good luck.