It's mainly Instagram that bugs me. I really dislike the green.Some devices you can set the led colour per application. So you have to open the app (whatsap for example), find settings, notifications and you'll see the led colour options.. Not all apps allow this, depends on the developer...
Light flow works just fine for me? I mean, I don't think there's anything such as a global switch but just setting the color to white for all apps should do.