Find my review of the original Halo (I'm NC25 and found a perfect match in Light) and you'll see I am madly in love with it. I'm not a Smashbox fiend by any means, so I had no idea there was even a color correcting version. When I discovered it, I knew I had to have it.
Halo Yellow comes in a smaller container, and instead of the flip up opening, comes with a twist-off lid. The shaving system is still there, which I love, because I can really control how much I want to use, and there's virtually no mess when I travel.
For fairer girls who found Fair too pink, and Light to be just somewhat off, Yellow should be perfect. It doesn't work extremely well as a color corrector - it just doesn't have enough pigment. Yet as a finishing powder it's wonderful, because while it's very yellow in the pot, it's actually got a transluscent finish (with a yellow undertone). This doesn't diminish redness on its own, but certainly helps (on a scale of one to 10, it's probably a four).
Having said that, if I use my Sonia Kashuk flat top brush, I can pack on this color where I'm pink, then buff out with a larger powder brush. This method takes longer, and I have to make sure I'm really moisturized, or else it looks artificial and obvious. But it works.
At $45, is it worth it? Probably not for everyone, but the mix of this and the regular Halo in Light works for me so well that I'm getting my money's worth.