Sometimes in a scene I have colored lights appearing on the edge of the screen. This happens from time to time, even in scenes that only contain a directional + skylight. I have had this happen on multiple computers, however all of them run an AMD RX480 graphics card.
For reference see the image
Hi BrokenInglish,
This has been documented already in this post: Emissive Colours bleed into viewport - Rendering - Epic Developer Community Forums
I added the information about this occurring in the viewport in a private comment to the devs in this Ticket: Unreal Engine Issues and Bug Tracker (UE-39945)
However, we were already aware of this information and have a JIRA for it as well here:Unreal Engine Issues and Bug Tracker (UE-39437)
Your case was different (cascade window) and needed a separate report.
I’m closing this post as a duplicate in order to keep the AnswerHub more organized.