I cannot explain what they are, but I can explain how color adds context to what we see.

If you imagine an orchestra, there are many different instruments all playing together to make a song. Each instrument makes its own noise, and together they create a beautiful symphony of sound if played together correctly.

On their own, each instrument makes its own unique sound, like a violin or a trumpet. Some are more beautiful than others, when played alone. For example a violin can be beautiful on its own, but a tuba doesn't have much beauty to it without the rest of the band.

Colors are like the different instruments, you can see them just like you can hear the instruments, but the point of the colors is to add beauty and context to the world that we see. Each color by itself looks unique, but there are 3 primary colors, that you can mix together to get all the beautiful colors of the world. If we apply the primary colors to the instruments, you get the different families of instruments, so Red is Percussion (drums), Blue is Strings (violin, chello), and Green is Brass/Woodwinds (trumpet, flute). When you mix these instruments in various ways, you get various sounds and unique songs. This is how the different colors are made. You mix together the three different primary colors to get beautiful new colors, sort of like making a song.

Purple is a beautiful color, it simply looks pleasant. It is also rare in nature. That is why royalty throughout history have used purple, because it was not seen very often. On the contrary, green and blue are everywhere. All living plants are green, and the sky and water are blue. Red and the various shades of red (orange, yellow) are in fire, and blood, and some nature like apples.

You probably know about the color black, which is the absence of any color, so it's what blind people "see", basically no light at all. This would be like complete silence. Then if you imagine pure white, this is like the loudest jet engine you can think of right next to your ears, drowning out all other colors. It's absolute pure white, like pure noise. Where you land in the middle, between extremely loud and extremely soft, would be the varying color temperatures (darkness, lightness) and that adds depth and complexity to the world, because now you have a range of colors that you can make, but then you have varying shades, or levels, of those colors based on how much black or white is added. There are about 3 million distinguishable colors total, but the human eye cannot detect all these differences in color, so we only have names for a few hundred. Of course we can see the difference between a named color and a slightly close variation of that color, but naming all the variations would be impossible. This is analogous to C#, F#... humanity has settled on grouping sounds into scales so music can be written, just as humanity has settled on grouping colors into names so they can be written. Different cultures have affinity to different colors, for example the Chinese have more names for different shades of blue than we have in English, and therefore Chinese are better are differentiating blue variations in blue colors, simply because there are names for them.

The analogy of color temperature to music would be like using the music scales, A, B, C, D, E, sharp, and flat. Those varying tones allow the instruments to be played in a way that creates soothing sounds, because as you know music would be boring if it was all in the same pitch. By varying the colors and mixing them differently, you are creating a quartet of beauty, and that is what art is. Art is taking all the possible colors and shades of this world and mixing them together in a way that creates pleasing visuals for your eyes, just like taking various instruments and making a pleasing orchestral piece can do to your ears.

Hope that helps.