Sarcastic White is a theme for Fastmail that changes the original appearance to a dark blue-ish look and feel. We've created the theme with a clean and uncluttered design pattern in mind, to achieve optimal focus and readability for code, syntax highlighting and UI components.
Install Sarcastic White
Go to Settings in the Fastmail webapp
Click Display options
Scroll down to Color and paste the following: #94b7e1,#5e82ac,#5e82ac,#94b7e1