Because I'm bored, and maybe you're bored too....

One reads that some birds see four primary colors, because they have four sets of color receptors. I don't think this follows though, logically four cones could easily map to the same colors we see without any loss of specificity. And our "three primary colors" don't correspond to our cones anyway. (The so-called blue cone is actually in the violet range, what we call blue is a combination of 'blue' and green cone stimulation, and yellow is a combination of green and red stimulation. And 'violet' looks purple only because violet (short wavelength) is not stimulating the green cones, which tells the brain that there's less green than there would be in white light, so that's interpreted as a slightly reddish blue even though there's no red light involved at all.)

So here's my challenge: Find out what the world actually looks like to a bird, by getting in a birds head a little bit while dreaming. Things are going to look different than they do to us, since they see shorter wavelengths. But the question is does the bird actually see a color that's totally different from any color we see, irrespective of what wavelengths they map it to.

Most of us have dreamed of flying, and I think Sivason mentioned seeing a color that has no waking life equivalent. I've seen shades and intensities of colors in dreams that aren't possible for me in waking life, though they're still the same basic colors, just brighter. I've also seen geometries that aren't possible to imagine in waking life, because they don't embed in our space, and I've seen an area as if I was in the space around it, instead of seeing from a single perspective as through a lens. And I've experienced myself being various animals, as have other people. So it seems to me that somebody should be able to do this without doing anything radically different from what already seems to be within our realm of experience.

Presumably its going to be hard to remember what the extra color looks like, if it exists, since we don't have the physiological equipment to deal with it. But you can still experience it as the bird, and hopefully get enough lucid objectivity on it at the moment that you're sure its really a new color, and you're not just telling yourself that you're seeing a new color when you're not. Then you can tell us 'yeah, I saw another color', or 'no, I saw only the usual colors, but things looked different', and maybe we'll believe you. Or maybe it will be easier for us to have the same experience once you've done it.

As a bonus question, see if you can experience what dark yellow would look like. Humans don't see dark yellow because its hard to stimulate the green and red receptors just a little bit in an environment that has enough ambient light to see clearly. Or maybe there's also another reason yellow isn't dark that has something to do with yellow and nothing to do with light spectra.

In my experience, it isn't necessary to be able to do any of this under your own power of will, if you're open to being helped a little bit. So have a little faith and see what happens maybe.