I doubt you would have any trouble mixing them. I have used new, freshly painted dekes mixed in with old faded ones without problem. Also, if you look at the live ducks, often times clear up until mid-season or later you can often spot drakes in their eclipse. I have seen drakes that you have to look closely to really tell that they are not hens.
I would imagine that the later in the season, the more of an impact the faded ones might have, if any at all.
If you don't want to mix them, I'd be happy to take some off your hands for you. :wink: Otherwise, use them and enjoy the shooting.