It's true that blue light delays melatonin production, that part is well established. But I think the effect gets overstated, because the real problem usually isn't the color of the light, it's what the screen has you doing.
Reading the news in bed or scrolling through an argument keeps your mind alert regardless of the light itself. Listening to an audiobook at the same brightness is far less disruptive.
So it's not just about turning the screen off, it's about how much the screen is engaging your mind. Dimming the light helps, but changing what you're consuming makes a bigger difference.