I am surprised that a well known name like Krell would mix components within a single unit, but if you don't hear a difference and it was factory done, I guess it's no harm no foul.
I would have expected a manufacturer would just use all black caps of the new line in making a new amp and save the extra blue caps for incoming spares to be used on amps to be serviced that used the blue caps.
I would have expected a manufacturer would just use all black caps of the new line in making a new amp and save the extra blue caps for incoming spares to be used on amps to be serviced that used the blue caps.