As suggested by a user on the Gaia Dimension project page, consider having skies have full customisation.
Currently, the Skies have two options: Changing, or Set. Changing means that the sky colours will change based on what biome one stands in, while Set means the sky doesn't change. When the Skies are using Set, the player can change the colour of the sky based on Biomes through another config option. However, these options are limited to existing biomes, and the suggestion is to make it fully customised.

To start, the config option to determine shifting skies should be set to false.
Then, using the sky enum, set the option to CUSTOM. This will make it so that the options are based on more config options.
There is a list of options: Red Sky Value, Green Sky Value, Blue Sky Value, Red Fog Value, Green Fog Value, Blue Fog Value, and Display Stars.

Note that this plan may be changed depending on whether having varying values in an enum is allowed. Hopefully so.

As of MC 1.16.2, sky colour is now determined via biome json. Soft transitions between sky colours appears to be out of the question, and stars can now be configured per biome. This is basically resolved.