While I think Marine Beam make excellent products, if you check the LED bulb finder here at Sailboat Owners:
http://shop.sailboatowners.com/cu/detail-led.php you can help support the forum.
That being said, before I knew of this site's LED bulb finder page, I think I found drop in replacements for my Perko bi-color bow light from cruisingsolutions.com, and replaced my stern and steaming lights from Dr. LED (probably from Defender.com) Dr. LED had a history of quality issues. So far in 2 seasons of fresh water (hardly difficult conditions) I've had no trouble.
If you are replacing a bi-color nav light, it is my opinion that you should get the warm white color, because the color value is closest to an incandescent, and therefore your red/green will actually look like red and green. If you use the cool white, they will come out looking wrong. Since I can't stand the cool white LED color, I also chose to use warm whites on my white nav lights, because to me they still look like nav lights. But I'm turning into a grumpy old man (so people tell me) so there.
From a liability standpoint, you are probably better off replacing the fixtures with USCG compliant fixtures from Hella or Aquasignal, those two being the only ones I know that advertise USCG compliance. While your LED replacements may look like the original incandescents, in an injury or death situation, it's possible that an attorney will make hay with the fact that you modified your nav lights, and therefore someone walks free on a technicality. Based on my assessment of risk, where I sail, conditions, etc, I feel ok taking this legal risk.