Board Thread:Questions and Answers/@comment-24063199-20140225120810/@comment-5247133-20140225121947

Affinity are the ones who deal Positive and Negative hits, you can look at your weapon for the Affinity, 5% means Positive while -5% means Negative (I know you know). Also:

Red Slash = Positive

Purple Slash = Negative

That's pretty much it.