eli5 What makes the color green, green?

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Hello all,
I am working on a project that requires me to identify what colors are green. This seems easy enough but I am working with color codes and don’t know where certain colors start and/or cut off.
I am working with RGB and a color can appear completely red with a value of 1 for Green but not appear green at all. Would this still be called green?

In: Physics

There is no hard and fast rule; colour labels are applied to light of a range of wavelengths. So green is typically between 495-570nm. Some languages don’t have a specific word for green, so that all might fall under one term with blue, and some will break that part of the spectrum into yellow-green, green, blue-green etc.

In the RGB colorspace, “all green” is 552 ± 1 nm (I’m remembering 552, and I can’t seem to find the reference right now).

When you have green at 1 and the other colors at 0 you should have green, or your display is malfunctioning.

When you have green at 1 and red at 1 and blue at 1 you should have white, or your display is malfunctioning.

So, just because green is 1 it isn’t supposed to imply the result is green.

No, a color that has any amount of green light in it is not green automatically. If that was the case white, all manner of shades of gray, and as you note pure red but with 1 out of 255 in green would all be green.

The issue is that this is just a question where you cut the color spectrum in to discrete colors. Many cultures will disagree wildly on what color is what color, and many don’t eve have a single word for ‘green’, instead lumping it in with shades of blue to create what linguists call ‘grue’. The of course there are the edge case colors that sit between two colors where you may claim blue and I claim green.

There are no absolute rules. You’re going to have to make a value judgement based on the requirements of the project in question.

Colors are subjective. There are lots of edge cases where different people will categorize the same color code as belonging to one of several color groups. The same color might be considered yellow or green depending on who you ask, for example. What I would do is to transform the RGB color codes into HSL or HSV codes. It is then easier to compare the hue from this as this tends to give a more consistent result. You should also check the saturation and luminocity to check for gray, white or black which do not have a specific hue.


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