You have probably seen a million comparisons but here is mine. I swatched these two together as soon as I received my Mac CYY order (I might have purchased 3 hehehe).
I am still happy I finally got CYY, but at the same time I was a bit disappointed it was too similar to Mac Dear diary, also a LE, but I already own. That's ok, I just wanted the real CYY to sit there next to all my pretty lippies :)
Candy Yum Yum in day light
Left: Candy Yum Yum Right: Dear Diary
I have also seen other comparisons of CYY to Barry M and Sleek, even to Maybelline and Milani. I don't own any of the dupes, so I can't verify that for sure. Either way, I am glad drugstore makeup companies are stepping up their game and including more 'unique' colors in their range :)