How do I change Sourcetree icon shown in Dock?
If anyone is interested, the issue was Pride icon on SourceTree app. I've found the solution here: https://community.atlassian.com/t5/Sourcetree-discussions/The-way-to-change-icon-for-Sourcetree-app/td-p/1110914


Go to https://github.com/alexzielenski/ThemeEngine
Switch to releases tab (I took the latest pre-release)
Download .zip and extract it
Open the Sourcetree.app with right click - show package contents and navigate to Contents/Resources
Copy Assets.car and sourcetree.icns to any folder
Run ThemeEngine from the zip in step 3
In ThemeEngine click "Open Document" and open the Assets.car
Find the icon named Pridetree
Open sourctree.icns with your preferred app - I used preview. Clicked on second icon pressed cmd + a to select whole image and pressed cmd + c to copy it.
Clicked on first image in Pridetree ThemeEngine and pressed cmd + v to paste it.
Repeat with second image. 
Save the document
Replace Assets.car in the app Contents/Resources with modified Assets.car.


Do not forget to backup your files. Your are doing this on your own risk as I do not know if it actually breaks the EULA.