I change the appearance to how I like my IDE. (1.8.10)
Thought I would share: Preview
I have only edited the *.SVG & txt files not the *.png files.
So I don't know if it will work for all?
I have windows 10x64.
If any like and want to try?:
Backup your "theme" Folder, found in something like: C:\Program Files (x86)\Arduino\lib\theme
and replace it with this one: Tims_Cool_Blue.zip
If it don't work, you made a backup of you original Right!