If you are affected by glitter dust and then decide to become invisible, shouldn't the glitter dust become invisible and no longer outline the creature? The source of light still exists, and the light is visible, but you cant see the source of light anymore.
You're not the first to wonder about this
The designers have known for a while that there are questions surrounding the scenario in which a creature affected by the spell glitterdust casts the spell invisibility. Pathfinder lead designer Jason Bulmahn clarifies (to some extent) in this 2010 thread:
Glitterdust kills invisibility and all the rules that go with it.
Glitterdust has no effect on other forms of concealment.
Glitterdust also makes it very difficult to hide and might blind you.
That is all... (as it is currently worded).
To summarize the most common reading:
Invisibility makes light sources but not the light itself invisible...
In fact, the spell invisibility says pretty much exactly that:
Light, however, never becomes invisible, although a source of light can become so (thus, the effect is that of a light with no visible source).
Thus an invisible creature's torch still sheds light.
...So invisibility makes glitterdust's dust invisible but not the sparkling
A cloud of golden particles covers everyone and everything in the area, causing creatures to become blinded and visibly outlining invisible things for the duration of the spell. All within the area are covered by the dust, which cannot be removed and continues to sparkle until it fades.
So the spell negates invisibility because the sparkling itself doesn't also become invisible.
The dust still glows, even when invisible; which makes it really very easy to see where the dust is. If it's all over an invisible creature, that creature is going to be outlined in light, giving away its exact position. That's half the point of glitterdust.
(One could also make the argument that glitterdust is a spell effect and not really an object that can be turned invisible anyway. I'm not sure it matters - it's dust, you can't really see the individual dust particles anyway, except for the fact they double as strobe lights.)