Weathering modern armor tracks

I would go with a dark gray finish, a wash of dark brown, drybrush with steel and then a dusting of "dirt" style pigments, Really no rust on new tracks unless the vehicle has been sitting a while, then only fresh bright orange rust.

And try to play down the differentiation of color between elements, like the tires vs. the tracks. Pigments are great for that. After all, they've been side by side in the same environment. If you imagine a truck that's just been offroading, or Karl on his bike, it/ he is pretty evenly coated, but not covered, in road dust.

I use exactly the same approach as I do for WW2 tracks. Some of those do have rubber pads, I just avoid getting any of the steel dry brush on the pads.

Yup. In truth there is not much difference material wise between WWII era Sherman tracks (the rubber types) and modern era tracks used on an Abrams. Your weathering should reflect the environment that you are representing. Mud & dirt for Europe, sand & dust for the desert. The longer any AFV is out in the field, the more it becomes covered in that field. Any rust formed on the bare steel areas is worn off as soon as the AFV is on the move again. But, one small detail missed is that rubber track pads and road wheel rims will get pitted and gouged in service. Particularly over rocky terrain.