It's the stripes.
Part of the essential beauty of the Packer uniform lies in its repetition of themes - the pants match the helmet's colors and striping. White stripe between two green stripes against gold. The same pattern is repeated all over the Packers' uniform.
But on the road jerseys, the stripes are a mismatch.
I don't know why they made that choice - I'm presuming that the team thought gold against white didn't provide enough contrast, so the outer stripes were changed to green, and everything else flowed from that.
This could have been easily solved by putting thin green stripes around the outer gold stripes, similar to what the Steelers do with their gold stripes:
See? A touch of black, and they can keep the standard striping. Not so hard.
This Packer sleeve stripe pattern is one of the last vestiges of Forrest Gregg's 1984 overhaul (the subject of a future post, no doubt). It's also terribly ugly, as were most of Gregg's uniform "improvements." I really can't stand those little white stripes around gold.
Personally, I prefer the classic Lombardi look for the road whites: