Originally Posted by LLC RI
My guess would be the reflection of the light against the copper interior of the shroud. This is probably more evident to you because the light is close to a surface which it is illuminating. In other words, you wouldn't see the orange tint to the light if it was uplighting a tree for example.
My only thought for you if no one sees the mouth of the fixture when it is lit is to get some tin flashing or some other durable and reflective material and make a cylinder that fits into the snout of the fixture, trim it to conform to the angle cut, and that should eliminate the orange glow.
You could also try taping off the lens with blue painters tape and hit the interior of that shroud with some gloss white spray paint. If you were going to do that, I'd say to use some 150-220 grit sand paper and paint.
Sounds like a lot of extra work.
Nightscaping powder coats the interior of many copper fixtures or shrouds. Some guys like the stock glossy white, others order flat black to minimize reflection.