Hey! I have a comparison for you guys that I did a super long time ago. As a matter of fact, I've had the draft of this post saved for a year now. Horrible, I know! You can tell it's old because it doesn't follow our usual photo format (and my nails are much longer then). So sorry about that! I didn't want to waste the swatches so decided to post it anyways.
This is China Glaze's Tempest with Sally Hansen's Grape Going. However, I'll probably do this comparison again one day since we now have RBL's Scrangie and I want to compare that with Grape Going. I've heard they are extremely similar.
All of these swatches were done with no base coat or top coat.
Tempest - This is a blue/purple douchrome.
Grape Going - This is a purple with bluish shimmer.
Application: These were all 3 coats. I liked the application of Tempest better than Grape Going. But that is only because I don't like the brush shape for this line of Sally Hansen polishes. The brushes are way too fat and uncomfortable!
Verdict: No dupes. Tempest is clearly darker than Grape Going. It's much more noticeable in the sunlight pictures.