I've recently updated to Mojave and I noticed that
a TextMate theme I use called iPlastic doesn't allow a transparency for
the background. For the same background setting in High Sierra the
background now is solid. I've tried modifying the theme directly in the
Bundle editor and tried different color codes for the background entry,
background = '#EEEEEEEB';
before the OS update, but I haven't been
able to add any transparency. Does anyone have suggestions?