That purple iridescence isn't normal? My dark pied Black Shoulder has a lot of that depending on lighting. It goes from purple to green and is just gorgeous.
Our guys here are all IB and they can have strikingly different iridescence in their train depending on the light; purple, pink, bronze, gold, it's quite surprising sometimes! So, yes, purple iridescence is normal even for 100% IB. Just another thing to love about peas...