pansy and viola colour reversion

I'm rather surprised to see both pansy and viola flowers reverting to a similar colour and happening on existing plants rather than self-seeded ones.

These were supposed to be a black pansy, Blackjack (I actually labelled these properly when I planted them last year - sometimes I forget).

These were Viola Floral Powers although I'm not sure if they were an existing plant or a self-seeded one that grew wholly this year.

I now know that the Chiltern Seeds pansies that I complained to them about that were not the colours they were supposed to be had all reverted to a similar colour. Surely they must have recognised that. I didn't know about colour reversion at the time.