I finally got a tempered glass protector that works! I won't repeat the whole story because I posted it in an Amazon review. I am a thorough reviewer, especially of products that work well. Here's my review.
Honestly, I don't know what they did to fix it. It's been several days and no rainbow.
OTAO - Galaxy S8 Plus Tempered Glass Screen Protector [Update Version], Easy Installation OTAO [Case-friendly] Samsung S8 Plus Tempered Glass Screen Protector with Installation Tray For Galaxy S8 Plus
I think they are still selling the one that didn't work for me. The new one is $11.99 as of this post. Get that one.
Honestly, I don't know what they did to fix it. It's been several days and no rainbow.
OTAO - Galaxy S8 Plus Tempered Glass Screen Protector [Update Version], Easy Installation OTAO [Case-friendly] Samsung S8 Plus Tempered Glass Screen Protector with Installation Tray For Galaxy S8 Plus
I think they are still selling the one that didn't work for me. The new one is $11.99 as of this post. Get that one.