I haven't messed around lately with custom colored emissives, but if I recall correctly, I'm pretty sure you need to set the color temperature "K" to zero so it displays the proper color. Then the light color it gives off will be the specified emissive color instead of that dictated by the K-scale value. I had a hell of a time figuring it out a while back when I was trying to make greenish glowing uranium glass in the presence of UV light.