Comment: The Kimberley - A quad expedition along the remote Drysdale and Carson

Mick
Possible explanation for difference in the appearance in the grass where the old tracks were may be due to soil compaction. Cattle also use the same tracks, so between vehicles but particularly cattle they compact the soil which reduces soil moisture holding capacity and may also limit root penetration. This causes plants to grow at different rates as the grasses in compacted areas are more easily stressed, flower more quickly and may have less vegetative density and or leaf to stem ratio.
That is why recently large scale farming operations drive over the same tyre tracks every time with their GPS, to minimise whole padock compaction, improving paddock yield.
I have seen the effect in paddocks where old farm tracks are no longer used and have been reincorporated into the paddock.