I think the Colorado Survival Gear DLC might have been a pre-order bonus. Steam has since started selling this DLC as a separate purchasable product, but not GOG.
From what I can tell, the season pass does not include this particular DLC. Which means that on GOG, the Survival Gear DLC is exclusive to the Colorado Collection.
So my message to people who already own the game on GOG and don't want to pay full price for a bundle just to get a measly item DLC is this: Contact GOG and inXile and ask them (politely!) to add the Survival Gear as a separate DLC on the GOG store.
If you don't already own the game, I strongly suggest buying the Colorado Collection, since it includes everything and it's also priced reasonably.
EDIT: Took out a bit where I whine about the vastly increased price of Wasteland 3 on GOG compared to Steam - the GOG prices have since been lowered and are now on par with Steam's prices.
Post edited October 07, 2021 by Exsurgent