As a mapper, I know that purple light cannot be produced by anything but a light that's RBG scale is purple. In real life, reflections could cause this, but not in Reach. You can see glares and reflections, but it does not shine onto anything else (such as spartans) (or can it? Please correct if wrong). This means that there IS a purple light there, that's intensity has either been set to very low, since you have to be in a small area for you to turn purple, or the light is penetrating that door, and there is something behind there. You know, it's actually probably possible to get a mongoose, warthog, or ghost up there. I suggest we invest in this, I believe there is something beyond that door.