The technique used to animate many objects in older films is called Stop Motion, but make no mistake this type of animation is still viable and used today. Stop Motion, also known as Claymation (stop animation using clay), is a form of animating an object frame by frame. Lets look at how it works.
It is true that when O’Brother Where Art Thou was filmed that all of the grass and foliage was green and had to be changed digitally for the movie. The best part about this question is that everything that one would need to perform this effect is available in the Digital Commons and I’m going to show you how it works.