Colourcode - Find your colour scheme
Rainglow Color Themes - 320+ color themes for a variety of editors and software.
Coolors.co - The super fast color schemes generator! Create, save and share perfect palettes in seconds!
eM Client - eM Client is a fully-featured email client for Windows and macOS with a clean and easy-to-use interface. eM Client also offers features for calendars, tasks, contacts, notes, and chat.
Color Hunt - Curated collection of beautiful colors, updated daily
Slack Themes - Make your Slack pretty with custom themes