Thumb, Middle & Pinkie- Revlon Colorstay "Coastal Surf"
Index & Ring- Opi "No Room For the Blues"
Aaannnd they're certainly dupes in terms of color. They are so close that it's really not necessary for me to own both. NRFTB is from the summer collection of 2009, I think. I tried googling it and couldn't find any real information on it. I think Coastal Surf would be easier to find since it's available wherever Revlon is sold and it was released within the last year.
Formula, however, is a different story. The Revlon colorstay formula is thick but not goopy. Two coats of the Revlon was all it needed. And, if I'm being honest with myself, I could have gotten away with one careful coat. Opi needed three thin coats coats because it was thin and kind of runny. When it comes time to clear out the dupes in my collection, Opi will probably get the boot. I hope this was helpful in your polish buying decisions!