Colormind - Color scheme generator that uses deep learning.
Cloudflare Design - Preview palettes against UI elements.
pastel - Command-line tool to generate, analyze, convert and manipulate colors.
Image Color Picker - Image color picker and palette generator.
Contrast - MacOS app for quick access to WCAG color contrast ratios.
Sip - Better way to collect, organize & share your colors.
SRCERY - Dark color scheme.
Happy Hues - Color palette inspiration site that acts as a real world example as to how the colors could be used in your design projects.
The Hitchhiker's Guide to Digital Color - Light-hearted introduction to understanding digital color reproduction.
Pywal - Tool that generates a color palette from the dominant colors in an image.
Piggment - The gradient you have always wanted.