MacOS – How to force Xcode(or any other app) to be on dark theme while macOS Mojave’s setting is on light mode

Update: Chrome now fully supports dark mode in Chrome 73 and JetBrains IDEs support dark mode in 2020.3.

Since PyCharm and other JetBrains IDE's are made in Java, they will not be able to use the native macOS Dark mode. Any system settings you apply also most likely won't affect Java applications, unless the developer specifically adds support for it, which probably won't happen due to the complexities of using system features with Java.(I've made some apps in Java, and it's currently impossible to use the macOS Dark Mode)

Many native apps will support Dark Mode without the developer having to do anything, but some that use custom UI views and controls, like Chrome, will need to add support for it manually. Dark mode support for Chrome is in progress(see here). SourceTree also uses custom controls and therefore doesn't support Dark Mode yet.

To disable Dark Mode for MS Office only, you need to run a terminal command for each of the MS Office apps in question.

For example, if you wish to disable dark mode in MS Excel, follow these steps:

1. Quit Excel if it’s running
2. Launch Terminal (usually found in the Applications/Utilities folder)
3. Enter (or copy and paste) the following command: defaults write com.microsoft.Excel NSRequiresAquaSystemAppearance -bool yes
4. Now press return
5. Enter (or copy and paste) the following command: killall cfprefsd
6. Now press return

Now when you launch MS Excel it should appear as it it normally would without Dark Mode enabled.

NOTES:

• To do this with the other MS Office apps, just change the command at Step 3 so that it’s referencing the app in question.
• Each of the app names within the command must start with an uppercase letter (note the uppercase 'E' for Excel in the command at Step 3.
• For PowerPoint, the app name must be spelt as follows: Powerpoint (i.e. only the first P is in uppercase, not both Ps)
• To revert back to Dark Mode, follow the same steps but end the command at Step 3 with no instead of yes.