A good friend of mine, who's a doctor, is very well travelled, and he told me he's seen skies of different worlds take all the colors of the rainbow (and the grayscale to boot). I suspect that he might be pulling my leg, since he does tend to exaggerate on occasion. 

![The refreshing green sky of home][1]  
*The welcome green glare of the homeworld's sky*

So, is my friend lying or can the sky really be of any color (besides octarine)?

If the whole spectrum is too hard, I'm specifically (and in this order) interested in:

- Green
- Gray
- Purple
- Orange
- Vermillion (I don't actually know what color that is, I just like the name)

To clarify: I don't mean briefly for a minute, I want it that color a significant portion of the day. And no, it need not be Earth, and the system star can be whatever is best for your color-purposes. And no, you don't need to address all the colors, (I mostly care about green) but extra brownie points if you do.
  [1]: https://i.sstatic.net/DEwmB.jpg