It has a musical analogy- a blue note.

No such thing as an orange note, or red note.

I have all kind of LEDs on my equipment (red, green, yellow, orange and - of course - blue).
When listening in complete darkness I find green to be the least annoying, followed by blue. Red LEDs are real pleasure-killers.
However, I find that intensity is a more important factor than color.
As for displays, I think red complement well black front panels while blue goes better with silver.
The best LED I have in-house is the one from my Philips cordless phone: it's yellow-green but so faint that it gives almost no light at all: even in complete darkness it looks more like a green spot than like a light-emitting device.

I just bought a cambridge azur spinner and it has a blue led and display but I think it's a play on azure so I will forgive them of their blueness.

Man, am I bored at work or what.

You mean everybody doesn't listen to music naked, with their eyes closed?

I just wanna know which color sounds the best?

I had been saving this review for a thread in early April, but here goes:

Blue LED's produce more detailed sound. More emphasis on the treble. Yes, you could say a cooler sound is associated with blue LED's.

They mate well with tubes, helping make a combined system more neutral.

Red LED's are tend toward midrange emphasis.

Orange LED's make for a slight combination of midrange and treble warmth.

Yellow LED's really focus energy in that region.

Red LED's sound best when paired with solid state equipment.

With speakers like Quads, the sound can become too too.

Red LED's work well with horn speakers.

Orange and yellow LED's sound their best with speakers that roll off in the top end, like Lowthers.

Orange and yellow LED's don't mate well with horns at all.

However, Audio Alchemy used to get great sound from a combination of yellow and red LED's, so keep this in mind when doing your own system matching.

Green LED's are just not hi fi. The wavelengths are not complimentary and makes for a confused cool/hot sound that ends up just sounding veiled and artificial. Ironic, green LED's sounding the least natural.

One caveat, green LED's make MP3's sound better.

I'll wait until April to discuss which colors of Blu Tac and other tweaks affect sound.

Perhaps one of the manufacturers will investigate the possibility of creating hybrid color components. Maybe use orange LEDs in the preamp section and blue LEDs in the amp section.

I suppose they could put mulitiple LED colors that the user could control, but I think that would just add too much circuitry to the signal path and mess up the sound.

I hear Mark Levinson and Jeff Rowland are in a joint effort to design and build an amplifier that comes equipped with a user "mood ring" that can sense the mood of the user and will automatically alter the LED indicator on the amp. Nelson Pass has been consulted to over-come the obstacle of taking the interface out of the signal path. Matthew Bond is being consulted to provide interconnects and cable that will transfer the signal across a sandwich of opposing magnets that will allow the signal to reach speeds in excess of the ability to hear. Tentatively dubbed the "Super Duper Signal Accelerator."

These are exciting times in the audio industry.

My Moon Evolution gear has blue pilot-lights, which I find to look very elegant and soothing. These lights are a very beautiful and radiant cobalt blue, which to my way of thinking is actually a very "spiritual" and "emotional" color.

I happen to be interested in the healing and spiritual aspects of certain crystals, gemstones, colors, etc., and I've learned that cobalt blue (as well as deeper shades of blue) are often thought by psychics to reflect the deeper emotions within ourselves.

Most of us are drawn to high-end audio because we feel and share such a deeply pleasurable and soothing emotional response or resonance when we listen to gorgeous music. In light of this, I for one find these beautifully radiant-blue LEDs to be in harmony with the emotional and spiritual experience of music.

And, for those who may be interested in Feng Shui, it seems fitting that blue would be associated with music, because blue is a "water" color; and beautiful music tends to "flow" rather like water.

Miles Davis settled this debate decades ago.

You'll notice, he didn't call it "Kind of Red."

I think the absolute worst overuse of blue LEDs is on my Musical Fidelity Tri-Vist 21 DAC.

There are four blue LEDs lit at a time on the front panel, and they are the clear-lense "high-brightness" type. You can easily read by the light of these LEDs in a darkened room (they are almost as bright as an LED flashlight!).

Very annoying! I was getting headaches while listening, so I replaced the LEDs with diffused-lense ones, with resistors in series to reduce the brightness to a tolerable level. Now the brightness matches the softer blue glow of the feet, and I no longer need to drape something over the front of the DAC to hide the light when I listen!

KB