Yellow versus orange

Solution 1:

Orange is one of the newest colors, in that in most languages, it was still considered merely a shade of a different color (red or yellow) up until recently[1]. My favorite example of this is the pigment red lead, which isn't red at all, but bright, almost-neon "construction orange". And of course the hair color of most redheads isn't red either.

I don't have any similar examples for orange=yellow, at least not in English[2], but I could totally conceive of someone describing, say, a leaf as yellow, even if technically its color fell closer to the orange spectrum than to strict yellow.

[1] In English, early 16th century. The color was named for the fruit.
[2] The Hungarian word for a carrot is "sárgarépa" = yellow beet.

Solution 2:

It can certainly be a difference in perception. My wife is mildly color-blind, and we sometimes describe the same item with different color words because we perceive it differently.