Adobe Color CC - Generates color themes that can inspire any project.
Color Hunter - Color Hunter is a place to find and make color palettes created from images.
iWantHue - Colors for data scientists. Generate and refine palettes of optimally distinct colors.
Color Palette Generator - Enter the URL of an image and find its color palette
Image Color Summarizer - The web service provides statistics describing color characteristics of an image identified by URL.
Paletton - Color Scheme Designer