Here's a list of the base skins available from the development build gameplay and what I speculate each base skin color is (speculation is most likely off, so bare with me). Feel free to add your speculation below!
Skin Name - Speculated Color - Animal Gene
Base Skins
Death Valley - Sand - N/A
Salar Del Huasco - Dark Grey - N/A
Yukon River - Black - N/A
Mangrove Forest - Forest Green - N/A
Limpopo River - Rock-Brown - Forest Rain Frog
Svalbard - Red-Brown - Reindeer
Champlain Valley - Dark Green - Northern Leopard Frog
Great Sandy Desert - Light Sand - Central Bearded Dragon
Gambia River Basin - Purple - Purple Starling
Sonoran Desert - Desert-Red - Cochineal Insect
Qilian Mountains - Light Silver - Snow Leopard
Amazon Rainforest - Light Blue - Scarlet Macaw
Skin Name - Speculated Color - Animal Gene
Base Skins
Death Valley - Sand - N/A
Salar Del Huasco - Dark Grey - N/A
Yukon River - Black - N/A
Mangrove Forest - Forest Green - N/A
Limpopo River - Rock-Brown - Forest Rain Frog
Svalbard - Red-Brown - Reindeer
Champlain Valley - Dark Green - Northern Leopard Frog
Great Sandy Desert - Light Sand - Central Bearded Dragon
Gambia River Basin - Purple - Purple Starling
Sonoran Desert - Desert-Red - Cochineal Insect
Qilian Mountains - Light Silver - Snow Leopard
Amazon Rainforest - Light Blue - Scarlet Macaw