Here is a blog post which covers some impossible colors and provides a few techniques to "see" them. [0] Of course reddish green and blueish yellow don't have any easy visualization techniques.

My personal favorite impossible color is Stygian Blue. Something is so energizing about seeing a color you know shouldn't exist.

[0] http://www.luniere.com/2014/03/01/hyperbolic-orange-and-the-...