(( Well ShiningSanctum1,

I'm going to try to come at this from a completely oblique angle... as I haven't typed anything here in forever, and finally have a few minutes, when I'm not studying, to actually try to type something... instead of just reading stuff from my phone. 

Mind you my ability with light, physics, and astronomy sorts of stuff is going to be haphazard... at best.  Anyway, instead of looking at colors from a pigment perspective, I'm going to try to look at colors from a "light" perspective.  So... here goes.

Alright, coming at the question from a light perspective, wavelength size-wise, I think Red has the longest wavelength, with blue being the smallest.  But... blue light wavelengths are considered "High Frequency" whereas red is considered "Low Frequency"... meaning, if memory serves, blue has more energy than red.  To use an astronomy illustration, Blue Stars are super-hot, and offer a ton of energy as they conduct fusion and fission... while Red Stars are "cool and dim" by comparison. 

Now... this seems to be very much at odds with how the characters are displayed in the series.  The "Red" themed characters do tend to be more active, which goes against the "low-energy frequency" that red is supposed to be.  And the blue-characters tend to be more passive, which also goes against the high-power frequency that blue light is supposed to have.  Though there is the exception of Ruka.  He could also be seen as super-powered blue. (Almost "White" or Ultraviolet" you could equate.) And this could equate to a blue-star burning twice as hot and fast, and then collapsing in on itself.  Which... he kinda does, for the handful of episodes he is in.  Now, further confounding this issue is that you do have a white-star, in Akio's current fiance (who acts more like a white-dwarf, instead of a White Super Nova)... and two "purple" stars (Shiori and Anthy), which could be equated to ultra-violet (which oddly comes off as "black", unless you have the proper equipment to really view it... but the "black" could denote a lot of things, including black holes and absence of anything.  Shiori definitely seems to be... absent of something.)  Equally as curious, the yellow and green characters do seem to have traits of both (being both active and passive depending on the story arc, as if they seemingly have "middle" range energies and powers.  Even more oddly, the only green star I can think of is Betelgeuse (which I think is actually red or brown, as I'm pretty sure there aren't any true-green stars), which is an "armpit"... and Sanonji is treated in a smelly sort of manner at times.)  Though... with all the "minor" cast basically having brown hair the idea of hair-color reflecting light-color wavelengths does fit too.  As brown-light can be seen as a weaker, dimmer, slower form of red light.  And Brown stars aren't terribly known for their power or illumination abilities.  And most are dwarf stars.

Anyway, as an aside, colors are very dichotomous in meanings as a whole.  Red can mean a number of things from passion, to fire, to aggression, to chaos, to love.  For me, at least, I usually associate Black more with "Power" and "Leadership"... oddly, because of the idea of very formal outings being "Black-Tie Events", and all the high, upper-crust socialites go to those events.

So... I'm not sure if that actually answered your question or not.  But your question made me think of it. ))

ooops, completely forgot about this thread. This is what I meant with the chakras:



You can look more if you do some research. Colors vary a little bit from one sources to others (sometimes they include Ruka's exact hair color too lol) but it's pretty interesting, right?