Gmail App Window Customize TitleBar Color
This simple script allows one to customize the background color of the TitleBar in any Chromium-based windowed app (Gmail in this case).
Script injects the HTML tag ＜meta name="theme-color" content="#3B3D64"＞ into the header section.
Simply customize the above hex color code value to your liking.
This same technique can be used for other Chrome App windows where an undesirable TitleBar color is assigned.
If an exiting 'theme-color' tag(s) already exists, you need to delete them first by adding the following code line (one for each occurrence) just before the above 'var m =' line:
• document.querySelector("[name='theme-color']").remove();
Inspirational credit goes to: BigChungus @ https://talk.dynalist.io/t/chrome-apps-title-bar-color/7717/5
