Why is this emission surface giving off the wrong color light?

What is wrong with this light? It has a a white-color emission surface, and yet somehow there is also a light blue glow as well.

The only part of my scene that has a blue glow is on the other side of my scene. This light is in the wrong place.

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It looks to me like the blue is just the illumination of the light’s housing. If that mesh is blue (blue-gray?), then it’s reflectance and bounced light will be blue, under a white light source. Now, if you were to tint the light yellow, the blue housing would look greenish. It’s just how light and color work.

If you want to get rid of all of the blue, you’ll have to change the housing’s material color to black, white or some shade of gray.

If you just want to get rid of the blue ring (glow) around the emission object, I believe you’d need to adjust the modelling, or set the emission shader to be one-sided - since there appears to be no contact between the two meshes and the housing is being brightly lit from the inside.

There is another part of this scene that has a blue glow, with a sun lamp with a blue color beneath it.

Hmm. Well, you’ll have to provide more info… at least some screenshots of your lighting/shading/scene settings, or the .blend itself (can be stripped down as long as it still presents the issue).

Seems obvious that you’re using Cycles. Are you using Blender 2.80 or 2.7x version?