A Question to Danny About Color Theory

Here's one thing I never quite understood about RGB values on the computer. How come some colors are easier to find than others in a color field?

For example. if you want to choose purple, you have a pretty good selection of purples, all of which genuinely look purple.

Same for green.

For some reason though, it's really hard to find a decent orange.

Maybe I'm just being picky here, but to me the colors look darker and browner than orange. Even on the color slider on the side, the region for orange is considerably smaller than that for the other colors. Even yellow is more prominent, although it's pretty difficult to choose a decent yellow as well.

Now, it's very possible that I'm overanalyzing some colors over others. Perhaps it's difficult to find what could be considered a "true color" on any color field. If so, why is it so difficult? How come there are so many variations of a color that don't even resemble the color all that much?

Perhaps our minds are more adapted to the different kinds of greens as opposed to the different kinds of oranges. A color like green is very widespread. We see many variations of green in all sorts of plant life. We can look at a color that isn't even close to "true green" and think it's green. If we try the same thing with orange though, we may find it deviates more from our imagined "true orange." 

Today in class you were telling me about how we generally accept the color cyan as blue, even though it is not. Cyan, magenta, and yellow are part of a different set of primary colors. Yet, we assume cyan is blue and magenta is purple. At the same time, yellow is still considered yellow in all contexts.

Is this a misconception that stems from the way our brains compute the light absorbed through out eyes, or is it something psychological?

I don't know if these are questions you've already answered, but that's what I'm curious about.

Here is Danny's Response