Did a little hunting yesterday.
From OPI I found:
DS Coronation, DS amethyst, & OPI Ink
lachiva_5 on Flickriver.com.
The Swatchaholic's blog for more great pictures that capture the purple, blue and magenta of the duo-chrome!!
From Finger Paints I got a twofer:
Mistletoe Mischief & Top Coat
Polish Wasteland. She's got some amazing swatches.
AllThingsNails! to see this and many more beautiful swatches.
These are not my pictures, I DID NOT take them. Links have been provided for each picture from where I found them.