I spent a few hours swatching last weekend and managed to swatch all my Ulta3s. I believe I finally have every colour! Here are the remainders of the red Ulta3 polishes.
Fire is a really bright yellow toned red creme. It's so bright you could nearly call it a neon. It was a little sheer but nice and smooth, not gluggy This was three coats and taken in full sunlight.
Scarlet is quite similar to fire, it's still a yellow toned red, but this is redder than fire. This was also more opaque than fire, only needing two coats below. Taken in full sunlight.
Foxy russset - I love the name, and yes that's three 's's. This is a deep burgundy red with a gold shimmer. Opacity for this was much better than fire. This was two coats and taken in full sunlight.
Pepper pot - colour wise this is pretty much a creme version of foxy russset. This was two coats. Pic taken outside, but the sun was behind the clouds.
Sizzling red to me is your classic red polish. It's probably more on the blue side than the yellow side of the spectrum and that is how it differs from Scarlet, its bluer. It's a really lovely polish that just glides on. This was two coats and taken in full sunlight.
I just had to show a comparison here of sizzling red next to pink colada. They are very similar, with pink colada just having a few more drops of blue in it than sizzling red. This pic shows sizzling red on the index and ring finger and pink colada on the index and pinky.
Over all, I think there is a very good range of red colours in the Ulta3 collection.
I'm thinking of putting together a full colour guide of all the Ulta3 colours I have (currently 92, which includes a few 'same name, different polish' versions). That way you can see all the colours in one colour group all next to each other. Yes, I think I will do that, after I have posted them all here.