[burrhead]

I bet if you look at it in really good natural light you’ll see the metal is “purplish”. It’s not uncommon and comes about for different reasons. The chemical mix can be a little off or worn out, the alloy doesn’t “like” the particular bluing mix, the heat of the solution was too hot. Sometimes it takes years for the change to become apparent. It also happens with factory bluing; I had an early Remington 700 with a very purple bolt shroud. Some years ago Ruger had problems with some of their guns turning purple over time.

It happens. I wouldn’t worry about it.