Chloe, yes, the lens is AR-coated on both sides. I think that is probably the cause of the blue ring and lower-CRI beam. The AR coating may be acting like a prism, splitting different wavelengths of light to emit at different angles. On a high-CRI light, this is a Bad Thing. It seems to lower the CRI by like twenty points, to the level of a typical Cree LED.
I have other lights with AR-coated lenses though, and none of them make a bright blue halo. The worst is my JB RRT01, which has an extremely faint tertiary corona with a blue-ish tint, but I hadn’t even noticed it was there until I went around checking all my lights for halos.
djozz, you’re probably right about the resistor but I don’t think I can get at the guts of the driver. I don’t even know if I can get the pill out. I’m hopeful that I can at least swap the lens for something less blue though, since the specs state it has a user-replaceable lens. I think that means the pill is supposed to unscrew, though with just my hands it won’t budge. It’s probably glued in place.
I’ll probably try to contact EagleTac before attempting to break the glue. I’ve also asked the vendor if they might be able to check other units for the bright moon mode and blue ring, but I’ll understand if they don’t want to turn mint-condition stock into tested-once stock.