No, it's not. Although as many other scientific facts it is often being stretched beyond the extreme in order to use it to legitimize crazy theories and/or sell products. That is a very common practice.

Blue light used during dark hours alters our sleep rhythm because our brain "tunes" itself according to the surrounding environment and light. A blue light tells our brain "we're in the morning, wake up up!" while a soft yellowish light tells the opposite "slow down, dusk is coming". Exposing ourselves to blue light or light with lots of blue components (example: cold white lamps) during night forces our brain to work in a different way that is not the one it should naturally at that hours. Spending many hours a day in a similar environment very likely alter the sleep hours with some side effects. So would a blue led on a phone kill anyone? Not at all, and it wouldn't either harm or do any serious damage; it's just really annoying to look at, especially in dark environments, but surely wouldn't be as bad as using a 6000K lamp to light a bedroom or as a TV backlight.

Unfortunately blue leds are extremely cheap to produce, so that pretty much every consumer gadget, especially those cheap gimmicks from the Far East, use them profusely even in places where other colors would be, also functionally, more suitable.

> No, it's not. Although as many other scientific facts it is often being stretched beyond the extreme in order to use it to legitimize crazy theories and/or sell products. That is a very common practice.

As far as I've been able to tell, there's very little in the way of literature that actually supports the "blue light" claims, but quite a lot of things which just self reference to support it.

> Unfortunately blue leds are extremely cheap to produce, so that pretty much every consumer gadget, especially those cheap gimmicks from the Far East, use them profusely even in places where other colors would be, also functionally, more suitable.

Huh? To begin with, all modern LEDs are blue, if you see a white LED, it's a blue LED, if you see a red LED, it's a blue LED. This is just down to physics more than anything, it's also much more economical to produce the same chemistry and just use phosphors to emit the color you actually want.

Blue LEDs emitting actual blue light however are vanishingly uncommon in any product at all, I don't recall the last time I've actually seen one. If you're talking about white LEDs being used in products? Well then yes, they will obviously contain blue light.

> To begin with, all modern LEDs are blue, if you see a white LED, it's a blue LED, if you see a red LED, it's a blue LED.

It is true that "white" LEDs are really blue or violet LEDs coated with phosphors that glow white or yellow (RGB LEDS with independently controlled red, green and blue LEDs are rare and only used in things like color-changing light bulbs).

It is not true that "if you see a red LED, it's a blue LED". Red LEDs are still made with semiconductors that directly emit red light (and the same goes for green, etc.). You can look at the spec sheets for LEDs on a distributor like Mouser and see the material used for each LED. The first red LED I came across directly emits red light using AlInGaP. I have never seen a "red LED" that uses a blue LED to excite a red phosphor. That would be even more expensive.

Surprisingly, they actually are blue dies with red phosphor. Keeping all the colours the same forward voltage makes driving them a lot easier, as well as having all the colours in the same production process.

It seems conceivable that a red LED based on phosphor excitation could exist somewhere where having the same forward voltage for different colors was essential, but I haven't been able to find one.

Taking into account the different forward voltages for different LED colors is a standard part of designing an LED circuit. One of the LED data sheets I have on hand for some 5 mm LEDs includes a forward voltage chart with 1.9 V for red and 3.2 V for blue.

Do you have a part number for a red LED that operates by illuminating a red phosphor with a blue LED?

> A blue light tells our brain "we're in the morning, wake up up!" while a soft yellowish light tells the opposite "slow down, dusk is coming".

I have no idea where you live, but in my sunny location the sunlight streaming through my window that wakes me up every morning is overpowering yellow. I associate "bluish" with darkness rather because evenings do become "bluer" before becoming dark. In fact, I have a colour changing LED bulb in my room, and I switch to yellow lights if I want to work longer at night - I find it more soothing on the eye, while it helps me be more "awake". The whitish / blueish light of the LED actually makes me feel drowsy.

On computer screens, I find that whitish / blueish light strain my eyes more, and thus apps like Flux - that change the display to a more yellowish tint - is more soothing and less stressful on the eyes.