Super simple question

I keep finding gear of various colors. Usualy its just white, but once and a while i get a blue, or even a purple.

Whats the differnece?

White .. Just salvage
Blue Unlocks Minor Runes
Purple Unlocks Minor and Major Runes
Gold Unlocks Majors and Superiors

Super simple answer would be use search.

Blue is magical, it's a little less common than white. Purple is uncommon, so it's less common than blue. And gold is rare, so it's less common than Purple.