It never did. At least since i’m playing GoW (arround 2,5year). At that point these kingdom were never a best choice for explore-killing colored troops.
In Explorde before remake, you could encounter troop from neighbouring kingdoms, that’s why best kingdom for farming specific color was almost never the kingdom with arcane mono-colored traitstone.
Red used to be Grosh-Nah (big number of red troops between orcs and for some reason red dragons from dragon’s claw and red deamons from Blighted Lands were happily roaming arround).
Blue, was always Merlantis, as blue troops from Blackhawk and Swords Edge used to roam there.
For Brown it used to be Drifting Sands.
Adana for yellow.
Khetar was one of best for Purple.
Green… it was either Zaejin or Pan’s Vale - not sure, but troops from this two kingdom liked to roam into each other.
And i’m almost 100% sure of these kingdoms, as i used to do a LOT of explores (traiting new legends every day/two with grinding all traitstones (mainly 16 arcane’s) from explore), and took some notes of most common colors in these places…
Now, after remake it also never been the way it is now(didn’t do the numbers at the begining, but pretty sure Merlantis was top Blue, and Pridelands was somewhere where it is now or even below top 5 for Red) - every faction added to the game changes the numbers, every week troop/event troop also. New mythics and legends dont change much as they are skipped in my calculation.
Depending what color will be Khaziel Faction troops- it might fall from the top - if all 3 non-legends wont be brown, Drifting Sands will be better place to encounter Brown enemies.
One final note -> Grosh’Nak has red/brown(Lava?) Arcane traitstones, but most of it’s troops are red and green, it puts it in top 4 for farming red and top 5 for farming green. Higher than Zhul’Kari which even is a “Green” kingdom…
One person analysis counters what you used to call “common sense” in other topics
Common sense might be misleasding, that’s why i made this topic - these 6 tables might be usefull for newer players. I might even add info about Arcanes that can be farmed there (on the way).
Especialy that i’m planning on updating them with every new troops released.