I'm exporting from the FCP timeline using Vimeo's HD output options:

h.264
5000 kbits/sec
1280x720
Deinterlaced

I've attached two files, one is from the FCP timeline and the other is from Quicktime after I exported it.

Look at the blue background and see what's happening. Any ideas why or how I can better export this?

Thanks!

The banding of the blue colors? There's really not much you can do unfortunately. It's the bane of the downconversion process; when you're throwing away information to squeeze the file down something has to give and color depth is one of the things that goes away.

You could double the bandwidth on your compression settings but Vimeo/YT/whatever is going to re-encode it anyway when up upload it so the banding will return no matter what.

In fact, you can see this very type of banding even in cable/satellite programs; they've got to compress their programs also to fit all those channels into that single transport stream and the same result happens: You'll see banding in what would otherwise be smooth gradients. It's most apparent in sky or smooth backgrounds.

I always feel bad for the guys who shot Sunrise Earth; they went to such extremes to find these gorgeous locations for their sunrise shoot only to have all that majestic color destroyed in the compression process for broadcast out.

You probably wont be able to get rid of it like Robert said. One question is, are you seeing it in the master you export from FCP? If so, try turning on the highest render settings in the timeline - I forget the exact wording at the moment - I think its Render All Timeline as High-Precision YUV and see if that helps a little.