Hue bulbs (and any other RGB LED) can display (almost) any color perceptible to the human eye as it combines the three wavelengths of colors our eyes can detect (red, green and blue) and blends them at different brightnesses. The “millions of colors” sell comes from 16-bit color found all over the place in technology. Here’s more info: https://en.m.wikipedia.org/wiki/High_color
Same way a printer works, or color blending for that matter, with RGB or CMYK you can make any color. Primary colors and brightness. Greyscales and magentas are extra-spectral.
Another thing that's curious about these lights which also applies to your computer/smartphone display aswell is the fact that it's able to produce yellow color despite only having red, green and blue leds in it. If you open up a yellow picture on your monitor and look closely with a magnifying glass there's no yellow there.
Thats another thing I don't get. Itf you look at your tv screen real close its all red/green/blue. Every pixel/cell, how does it appear different from far away
Okay you really want to fuck with your mind, brown is not a color. You can't not break down a rainbow and find brown anywhere in it. There is no such thing as brown light. Yet you can see it every day.
Human eyes have three kinds of cells (photoreceptors) for color detection. They each react to either red, green or blue light. If more than one of those cells are activated, your brain interprets the light based on what cells activated, and how strongly they activated. If red and green cells activates, the light is seen as yellow. The light is seen as white if all of them activates fully.
This also means that light bulbs can produce white light by simply producing three wavelengths (colors) of light. The problem with that kind of “fake” white is that colors will look wrong under such light due to the way how objects reflects light. This is very common with low quality LED lights, and even the best smart lights aren't very good at it. When buying LED lights, you might want to look at the CRI (Color Rendering Index) value and make sure it's above 90, or as high as possible.