I vote for 3.

#3 makes your colors pop

What is a Flying Geese Rainbow quilt?

I would vote for number three.

i vote for #2

Number two is lighter. I think the other colors would pop better with that one.

I definitely vote for something neutral for the sky. If not mottled gray, then black, white or almond. The brightly colored geese will pop with a high contrast sky/background. Think of it this way, a brightly colored rainbow shows up against a mostly neutral blue sky, after the rain. Thats how the pretty geese will stand out on your quilt if you choose a neutral background.

I also vote for a more "sky" color to show off your lovely rainbow colors.

However I can also see if you are trying for it to be a rainbow against a sunrise or sunset sky then your reds make sense.

Of course it's your quilt and your vision of what you are trying to create! So you know best on that.

I would also go for more of a neutral so the geese pop more. But if you like the red, I would go with #3 as it has the most contrast with your red geese. Your three reds contrast nicely with all the other geese, so I would make the decision on which looks best with the red geese. Of course you have the best view for that.
Just my thoughts. I am sure it will be beautiful. Geese are one of my faves.....would love to see this completed!

IMHO, I am not keen on any of them. Do you have a dark forest green or dark maroon or black? Just try some more colors, even a midnight blue would be nice w/ the rainbow geese. The brown tones seem to over power the other colors in my old eyes:D.

If I had to choose one of these it would be the third one, it allows the geese to fly!
peace

EDIT: I also like the idea of a grey sky, but a dark one!