Creating a custom race is very limited game produces a .faction file but it cannot be edited if you want to make more changes that game allows.
In GC2 you could easily create your custom race and you could customize it even more by editing the race's file. Of course GC3 is a new game but so far things look more complex to be done. Creating my custom race is better editing FactionDefs.xml and adding my race there rather in-game and it's limitations.
Color options are ehm too colorful. There should be an option to customize all the colors both interface and ships.
Game uses definitions for colors and reads them from pre-defined color sets. For example "AltarianHot" R:80 G:215 B:255. RGB Colors are predefined in game core xml file. Means you cannot create exact the colors you want but choose one of the set or edit the core xml file or create a mod.. but choosing your colors should be easily done in game! That's too basic to be so limited!
Barren worlds are not colonizable it has been noted in forums.
I was offered a Starbase for free from a custom race, game crashed.
Info tips are still non-readable in several cases where they need for example 2 lines space you can see only 1 line space and half text from 2 lines. Example a planet with "Serene" text is half hidden.
Created a custom colony ship spent about 1.5hr saved and... nothing gone.. 