Change sound notification for text/mail in Samsung phone
For some reasons, Samsung chose to use same notification sound for all apps. It was ok but text/mail should be separated. By default sound and LED for mail&text are set to be the same (Blue). I don't think you can change the LED color using Samsung native control, you can only change the sound notification.
Goto Settings >> Sound and Vibration >> Notifications Sounds >> Choose the different sound notifications for text/mail/calendar/general.