For example, there are three eggs. The left egg is the largest and the front egg is leaning on its side. And from front to back, they are colored purple, yellow, and blue.
What? You do see purple, yellow, and blue, right? Uh... you don't? What colors do you see? Let's make sure that we are talking about the right file...

The result is pretty clear: I have one picture (a PNG) that yields NINE different color sets! (Ten if you convert it to JPEG and use LCMS to render it.) The colors that you see are strictly dependent on the specific program that you use to view the image. Even something as minor as calibrating your video driver or patching your software could alter how the image is displayed.