Provide a method for users to create and share skins for Bitwig’s UI.
What problem(s) would this feature resolve?
Color preferences are subjective, and different users prefer different colors to work. Also, users may get tired of the same colors, and they wish to change them.
Finally, some users just want a dark theme, which the current settings for Midtones and Black level don’t provide.
How does this feature fit in Bitwig as a product?
Bitwig offers many features to allow users to define their workflow and environment as they please. A recent feature allows users to define the colors of clips, which is a step in this direction.
Is there already an alternative way to achieve this on Bitwig?
No. A default.theme file can be accessed in any Bitwig installation, but its use is undocumented and community attempts to change the UI through modifications of this file haven’t brought any results.
Could it be implemented using Bitwig components or APIs, without Bitwig team’s support?
No.
Could it be provided by a VST or something else reasonably integrated with Bitwig?
No.
Are there other products that offer this feature?
Ableton Live, Reaper, Reason. Cakewalk, LMMS…
Relevant links (optional)
“Bitwish” theme for Ableton Live. 
https://www.reddit.com/r/Bitwig/comments/eymnfc/theme_skin_support/