Gotta love those pics. Mmmm-MM them T-35s look good enough to eat! And the MT-LBs and brand-new M4A1 early version Shermans are just spanking good.
As has been said, there is no "right" versus "wrong". You should do a little experimenting with various techniques ... as described here, or that you develop yourself.
I have spent a fair bit of time doing research on real tanks. Part of the same fascination that brings me to micro-armor and wargaming. What I've learned is that tracks come in two basic colors: bare metal or black. But tracks, on tanks in the field, wind up in one basic color: dirty/rusty. All of the techniques that you see here try to mimic this.
Most nations in WW2 used bare metal for their tank tracks. Soviet, British, French, Italian tracks should be bare metal.
The Germans evidently painted their bare metal tracks black sometimes, an approach which doesn't make a whole lot of sense as the paint was quickly worn off when the tracks were ground around in the dirt (as was their purpose in life). But spare tracks on racks on the tank may have still been black long after the actual running tracks had the majority of the paint worn off. This painting of black tracks seemed to be more common on smaller AFVs and earlier in the war. Half-tracks, Pz I, 2, 3 and 4. Tiger tracks appear to have been mostly bare metal. (I can easily accept being over-ruled on anything I say about German armor, as that is not my specialty.)
US Army vehicles sometimes had bare metal tracks. Most of the tanks that went to North Africa had bare metal tracks. The M18 Tank Destroyer used bare metal tracks exclusively. But most other US tanks transitioned to metal tracks with rubber pads during and after the North African campaign. And US Halftracks operated on rubber tracks (not even metal with rubber pads, but rubber -- overgrown rubber-band style) throughout the war.
(Most western AFVs have moved to rubber-pads in the modern era. But I shall focus on WW2 vehicles here.)
What I have observed is that all tracks (and most running gear) quickly accumulate a heavy coat of dirt and rust over most any bare metal or rubber. But then the wear of running the tracks wears off that coating, revealing the underlying bare metal or rubber.
So the general approach I use (as to many others, with approaches that may be similar or different) is to try to give a view of the underlying color on the portions of the track that would come into contact with the ground and or with the moving parts of the tanks, and leave everything else dirty / rusted.
For me, that means bare metal tracks are metallic silver, and rubber-padded or rubber tracks are black. And both are dirty/rusted.
Here are some examples of tanks I have known ...

Here is a Soviet T-34 with characteristic bare metal tracks.

The US Army M18 TD had bare metal tracks.

The US Army M10 TD had rubber pads on its tracks.

The US Army M5A1 Stuart had rubber pads on its tracks.
I seek much the same affect as mentioned by TStockton and Extra Crispy above. But my technique is a reverse of theirs.
I paint the track in its proper base color. For bare metal tracks that means a metallic silver. I currently use Poly-S "Graphite", which is a dark silver. I've used other silvers too. My favorite was Poly-S "Oxidized Aluminum", but I can't find that anymore. For rubber tracks (US halftracks) or ruber-padded tracks (most US Army tanks) that means black. I use Poly-S "Oily Black", which is black with a bit of gray and brown in it.
I then do a heavy wash of low-diluted Poly-S "Rust" on the track and the running gear. Sometimes for a desert vehicle I'll do a wash of Poly-S "Mud" or "Khaki".
Occasionally I'll do a dry-brushing of a lighter silver, like Poly-S "Chrome" or "Metallic Silver". But not always.

Here are examples of my results for bare metal tracks on a Soviet T-34 and some KVs.

Here is an example of my results for rubber traks on US Shermans.
So try a few. See what you like. Post some pics. We do love to see 'em.