In my post about the January 2014 Julep Maven box, I mentioned that Margot and Sienna struck me as being very similar colors, with Sienna appearing just a smidgen more silvery/unsaturated. Now that I’ve swatched them on the nail, I can confirm that they’re similar enough that they can probably be considered dupes of each other for practical purposes.
These photos are taken in indoor light. (I might add a sunlit shot later on.)
On the nail:
UPDATE 1/7/14: Here’s an extra shot in natural light on day two, with my phone camera:
Basically identical twins with just a few hard-to-spot differences to tell them apart, am I right? In person, Margot is slightly warmer and a bit sparklier in some light, so personally, if I had to pick one, I’d go with Margot, but I honestly don’t think anyone would notice the difference if it wasn’t pointed out. I stand by my earlier conclusion that you probably don’t need both.