Red is usuasally regarded as a color which visually leaps out. Red stand out. Red jumps off the page.
But does it really?
I found two interesting pictures on Flickr. Both contain a red button. The one button is highly visable, the other is almost hidden in its surroundings, even while it takes up a large part of the picture.

How come the one button stands out a lot more than the other? It's not because the button is red. It's because the background is NOT red. From a design perspective, that's a pretty important distinction...

Once again it's not about the colors, it's about how the colors relate to one another.