Some electromagnetic frequencies are colors, but not all colors are electromagnetic frequencies. That’s why parent stated that color is a brain phenomenon.
What do you mean? (Outside the detail that "hues" are electromagnetic frequencies, while colours are compositions - there I just simplified.) Which colour is not such?
I would explain it as colors are byproducts of electromagnetic frequencies, but they are qualia generated by your brain. There are many optical illusions that play with this fact. For example, in twilight, the frequencies you would call blue are different than what you call blue during daytime. This is because the brain /eye adjusts to the general light conditions. (As sunlight is generally "redder" at twilight).
If the colors were the same thing as the electromagnetic frequencies, then the same electromagnetic frequencies would be the same colors, by definition.
They aren't. For example, put a card of color A in front of a background of color B; now move it in front of a different background of color C. You will experience color A as being a different color (especially if colors A, B, and C are chosen to maximze the effect).
The electromagnetic spectrum returned by card A isn't different, but the color perceived is. Thus, electromagnetic spectrum is "out there", but color is "in here".
The original post claimed that «Colors don't exist outside of your brain»: such statement, while true, is false, as its negation is true (we have mentioned paraconsistency in this very page): "colours" do exist outside your brain, as their nature also is, in a way, being electromagnetic phenomena, function of frequencies.
While such ontological property is pretty common, it is just summoned with some force when someone claims "[fuzzy] is [strict]".
> Thus, electromagnetic spectrum is "out there", but color is "in here"
Of course. That just depends on what you want colour to be. If you put it conceptually near "electromagnetic spectrum", then the distinction emerges.
It is the sum of two ranges (magenta is the sum of red and blue lights): it also exists "outside", like the rest.
For that matter, not even "pinkish grey" is defined by simply a frequency (the hue is, the colour is not): the definition for this purpose was meant to be concise, not literal.
Your previous comment had stated that hues are electromagnetic frequency and parent comment showed a counterexample. Color is a complex phenomenon that cannot be reduced to electromagnetic frequencies and their composition. For an example, see impossible colors [0].
> Your previous comment had stated that hues are electromagnetic frequency and parent comment showed a counterexample
That was not the point, and said counterexample is not such (also magenta is, in a way, "electromagnetic frequenc[ies]"). Impossible colours - virtual colours - do go more towards the counterexample, though up to a certain point as they refer to the mental phenomenon of colour and leave the physical nature of colour untouched.
But finally I get what you meant when you stated: «not all colors are electromagnetic frequencies». True ("not all perception is produced by a direct influx of"). But also false, apparently (to the best of my), as objectivized hybrid colours are compositions of electromagnetic ranges; objectivized virtual colours are as well etc.
> Color is a complex phenomenon that cannot be reduced to electromagnetic frequencies and their composition
Yes, and nobody ever stated the opposite - no reduction was never implied, no «overlapping» (as written in the other post): the point was expressed, nearby, at https://news.ycombinator.com/item?id=31217999
What do you mean? (Outside the detail that "hues" are electromagnetic frequencies, while colours are compositions - there I just simplified.) Which colour is not such?