I don't ever really recommending doing this only because you can get a bleed through of the old color and not be able to see the true beauty for what this is.
For Audrey is a play on the signature Tiffany trademark color. However, to explain to you how little I know about fashion, jewelry and the like, I originally thought the trademark color was a royal blue, which is why I didn't understand this whole robin egg blue thing. /facepalm
I have real swatches though - For Audrey was originally my problem child - beautiful, but horrible to wear. The first time I tried it, it took me 3 coats and lots of crying before I smudged it all off. The second time was better - one 2 coats but the second coat was purposely thicker to cover up any streaking from the 1st coat.
China Glaze [official website] can be found online through several etailers, including my favorite Head2Toe Beauty [official website] or Sally's Beauty Supply [official website].