This brilliant colour is caused by IIV-31 (Isopod Iridescent Virus). I've been checking hundreds of pill bugs over several years for this unusual phenomenon and my persistence finally paid off!
Sadly, this total colour change is usually the later stage of the virus; once a pill bug is this bright it generally doesn't have much longer to live.
This guy was eating another bird.
Right after mulching
Saw this guy in the morning pulling down his web between two trees.
This little guy was hanging out right near a trail during the middle of the day.