Galaxy S6 Edge :: Underline Spelling Errors In Red

Since lollipop update my Note 3 underlines spelling errors in red. I hate auto correction but love the red underlining feature. You need to install google keyboard for it to work however you don't need to use google keyboard. Just have it installed. This feature never worked on note 3 until 5.0 update. I'm at an ATT store at the mall and I installed google keyboard in the s6edge but I cannot seem to get the red underlining to work? A screenshot would be great confirmation. I really need this feature. It draws my attention to possibly misspellings without changing them. I use a lot of jargon that gets "autocorrected" into jibberish if I use normal autocorrection.