sudo updatedb then
locate arduino or
locate theme.txt or a related search.
On my system, I see
theme.txt in the installation directory:
A related issue is discussed on this blog :
To make Arduino use the native Swing windowing instead of forcing the
GTK look and feel [...] change the following line:
#comment out this line:
#java -Dswing.defaultlaf=com.sun.java.swing.plaf.gtk.GTKLookAndFeel processing.app.Base
#change it to this:
If this is still relevant, you might be able to work with themes by changing GTK theming directly.