Me personally, I use Textra for texting, and BlackBerry Hub+ for emails.
Both apps can set the LED color. Someone above mentioned my exact same color scheme. I can set different colors for different email accounts in the Hub, green for work, and blue for home. And texts are purple. Since most of my texts are from my wife, I know it's almost always her.
I don't set the LED for any other notifications.
I tried one of the dedicated LED apps, but didn't care for it. Just the default works well enough for me.
This is on an S9, and had this on an S8 before that.