Well, If you'll forgive the reference, on Dan-Ball, Acid is an electric-lime green. So I can see three possible reasons:
[list] [*] The color was too similar to Dan-Ball's, so it was changed to something more original. [*] The color wasn't bright enough to relate to a stereotypical image of acid, so the debs made it brighter. [*] The debs simply did not like the color, so they changed it to something more favorable. [/list]
I, honestly, think the color is fine. But if you prefer the khaki color, you can always just use the Deco. Layer to alter its color.