Left to Right: Do You Lilac It?, Done Out in Deco, and Parlez-Vous OPI?
I had originally thought Do You Lilac It? would be pretty close to Done Out in Deco, but even in the bottle, they're totally different. Do You Lilac It? is much brighter and more saturated in color. It might be closer in color to Zoya Malia, but I don't own that one to compare. I think it would make a great pedicure color, especially for spring. It's the easiest to get out of these three, as it's part of the core line for OPI.
On the other side, Parlez-Vous OPI? is like Done Out in Deco's darker older sister. It even has the same dusty quality to it that Done Out in Deco does. These two are definitely in the same color family. I could totally see these two as a mani/pedi combo or even part of an ombre manicure. Unfortunately, OPI decided to discontinue Parlez-Vous OPI? (I know, right?!), so you may have a hard time tracking it down outside of internet stores. But if you can, you won't regret it. It's beautiful!
Bottom line: These are totally different enough to own all three. Yay! I'm just loving these colors right now, so I'll probably be expanding my collection of lavenders/lilacs.