It's kind of like how the default brick textures glow in the dark. Badspot has stated that there is probably no way to fix this.
I remember someone saying something about using a different shade of color, or something like that, for a set of prints so they don't do this. I can't remember what exactly it was though.
I don't think lighting affects decals and I don't think this engine supports the ability.
Well that can't be right, just look at the picture above, the only part of the face glowing is the hair. And none of the decal is glowing. At least some of it is affected by light isn't it?
All those parts are black. Black probably glows in the dark too we just can't see it because it's black.
transparency, perhaps?