I picked up OPI's "Dont Mess with OPI" on a great deal recently, and then spied Sinful Colors "Envy" while I was out yesterday. It looked so similar, I knew I had to do a swatch comparison. When I first tried OPI "Don't mess with OPI" I described it as Coleman Camping gear green. This may or may not have been the result of a Mike's Lemonade saturated camping trip I happened to be on with little hopes of sanity, but I love the color regardless.
Upon swatching, you can see that Sinful "Envy" has a bit more blue in it. Both are opaque and gorgeous after three coats, these are both without topcoat in the pics. They are close enough that you could save the money by just picking up the Sinful color, and get the...awesome...ring as well. ;)