I have heard of this before, especially from people who use lights for paramedic-type uses. As I understand it, the ability to "see" a person's skin colour tells you a lot about their true condition (blood loss, internal bleeding, etc.). Incandescent lighting apparently makes these changes stand out more than LEDs.

"White" LEDs use a phosphor-type coating to convert blue light to white. It's somewhat like the technology of standard fluorescent lighting. Every type of white LED has a proprietary coating; cheaper usually means more blue-ish, though that's not a hard and fast rule.

(On the other hand, the "cheap blue" LEDs make the eyes of night-time animals light up like a Christmas tree, from great distances, even when the light is very low-powered. Very cool to see two glowing eyeballs pointed at you from the better part of a hundred yards, when all else is darkness.)