For some better (I hope) comparison, I uploaded to screen shots of the paint ref site. The smaller window is of the colors from 70 (B3, B5, B7), 71 (B2, B5, B7), and 72 (B1, B3, B5).
First, I don't think the B5 was consistent between years. On that page, there are three totally different RGB codes, 70 B5 is
#285EA6 , 71 and 72 are
#33639B . The order code for 70 is different from the 71/72, while the 71 is the same as the 72.
To my eyes, the modern B5 (#3777BD) is the same color as the 70, but just....brighter? Maybe a touch lighter. Nowhere near the B7, but maybe/probably closer to the B3.
Strangely, and I know it's a trick of the eye because all the 2009 on up have the same RGB codes, the 15 looks much closer to the 70 than the 09/10.
Keep in mind, too, that's it is more of an 'inspired by' than a straight reproduction of the originals. Not just the color, but the whole car, too. It's a modern take on a classic
Not trying to be argumentative (I have a wife for that), just trying to give a somewhat closer comparison. I'd be happy with any B5, or '72 B3. They are definitely not 100% the same, but to my eye, the difference is negligible.
While I'm only (only?) 37, I feel like I have a similar feeling compared to the originals. 6 years ago, when I bought my Charger, I sat in the dealers cube, and right behind him was the B5 Challenger that I wanted. I barely took my eyes off it. Now I have the chance to actually get it, and I think that's got to be similar to the feeling the OG guys have when they think this is there chance to own that classic again.