There was an excellent write up on this on the old Bebi web site. I don't think it's up any more though.
I have a Bebi anchor light, actually I have the one that is supposed to be used in a tri-color setup, so it has something like 24 or so white LED's. It's always the brightest light in the anchorage.
As far as colors temperature goes, to be properly within the specifications of COLREGS Annex I, the acceptable LED color would probably fall within the neutral or warm white color temperatures. For most white LED's, cool white is a bit too much in the blue.
Does that mean that it's unsafe. I certainly don't think so. The reason that the USCG's regulations are what they are is simply because when they were written down, they needed to grandfather in all of the oil lamps and incandescent lights that were in use, which are always yellowish in tone, i.e. warm white. They just didn't need to consider a light source that drifted off in to the bluish tone a little. It simply didn't exist at the time unless one wanted to run an oxy-acetylene torch from the mast head. I've read that the Coast Guard is looking into this, but in the mean time, warm white LED's are becoming brighter and more efficient so the issue is likely to be moot before the rules are changed.
You still have to make sure that your brightness is above the minimum value for your length boat, and in your installation. That includes any lost illumination due to wiring losses and condition of your anchor light housing, so it's best over engineer a bit (or a lot

), in my opinion.