I live with what you are seeing. I have some 38 Spl WCC 93 and 94 cases which are probably just on their 10th loading that just done come completely bright and have some light tan blotchy streaks around the neck. (I got them as reloads from a great friend of my father 20 years ago and began using them about 5 years ago when I started.)
As long as they don't show pits or dark brown I load them up.
Corrosion is what you want to avoid. Dark brown from laying around on the ground too many days or signs of corrosion or chemical damage, like pits, end up in the scrap bucket.