Loot filters

So I’ve been using a loot filters for a wee while now but I’m a bit confused sometimes still on what to pick up and what not to pick up. So sometimes I see items that have T1-T5 on the end and I pick them up always but 9/10 it’s just garbage items. Sometimes items have orange borders round them sometimes it has red borders sometimes green. I don’t know if I just have really bad RNG or what but no matter when it tells me to pick an item up or not it’s just vendor worthy