So i came across an easily noticeable/reproductible bug with the paint-brush (which is much appreciated by the way for a little customisation!).
I painted my base green, and i noticed if i quit & re-load (no need to quit the program) some rooms go back to the default color. It is only the "craftbench interior room", "Chemistry Lab", "interior-garden patches", & "reservoirs" for the moment. I saw that is was always the same type of rooms that are problematic... (blank rooms, "fan rooms", "stockage rooms", and airlocks seems to retain their colors ) But they should all be tested! ʕ•ᴥᵕʔ
I guess it is only a variable that is lost in the saving-reloading process etc... should be easy to see & fix! ₍ᐢ•ﻌ•ᐢ₎