I'm trying to get the raid frames that's internal to Elvui to show my Renewing Mists buff as it spreads around the raid. I can get it to show as an icon / square 'dot' but buggered if I can get it to show with a solid border around the players unit frame. Doing this in standard grid is quite easy but unfortunately I can't get enough control over how standard grid shows its raid debuffs.
So you want a green border to appear around targets affected by Renewing Mist on your raid frames? I've been using ElvUI frames for awhile, and I don't think this is possible via Elv settings. You can change the green dot to a textured icon of the ability though.