So I'm looking for data and clarification as to what the different colors of items mean, and how they relate to the stat budgets on them.

Right now, based on a cursory survey, it appears as though there really isn't any difference in potential secondary stats between green, blue, and purple at the same item level.

Is the color separation superficial once you get past HQ White gear? Is the only major benefit to the Relic the fact that it's got fancy graphics?

Square, what do the colors mean?