For all of you do-it-yourself cover-makers, here is how James Gurney recommends for you to "handle" green in your covers.
The Green Problem Green is one of the most common colors in nature, but it has presented such a perennial challenge to artists and designers that many have banished it from the palette. Why is green a problem, and how can you solve it? There is no doubt green is a fundamentally important color. Many modern psychologists and color theorists regard it as a primary color... The human eye is more sensitive to yellow-green wavelengths than to any other, that's why the spectrum or the rainbow looks lighter in that section. Yet in the field of book cover design, there's an old saying that "green covers don't sell."--- Costume designers have said that green often looks ghastly in stage lighting. Gallery directors have reported that clients aren't attracted to paintings with a strong greenish cast unless it is handled correctly. Evidently this was an issue even 150 years ago, when Asher Brown Durand commented on "the common prejudice against green. I can well understand why it has been denounced by the Artist, for no other color is attended with equal embarrassments."