Sinful Colors is, in my opinion, second only to Brucci in terms of having a huge selection of awesome and weird colors for real low prices, and being sold at drugstores. It's an awesome brand.
Anyway, here's an amazing purple to green duochrome. It's one of the stronger duochromes I have, love it. Like many duochromes, it's pretty sheer, and I think it's best over a darker color- I used Brucci "Black Emerald" to bring out the green color shift.
Below is two coats over two coats of Brucci "Black Emerald" all with one Seche Vite top coat
Below is four coats on it's own. So different! More boring, I think...