So you are interested in learning what color is opposite of green on the color wheel? The quick answer is Red. You can clearly see this by looking at the color wheel below
Red is green’s complimentary color because they are opposite one another on the color wheel. Because of their high contrast, complimentary colors such as red and green can produce some very interesting visual effects when used in the same piece of artwork.
Here is an example of the red/green complimentary color scheme in action. You can clearly see how these two colors sing when placed next to one another.
I hope you found this post on what color is opposite of green on the color wheel helpful. Find more posts on color theory here.