WebGradients is a free collection of 180 linear gradients that you can use as content backdrops in any part of your website.

RGB颜色值与十六进制颜色码转换工具，能将RGB颜色值与十六进制颜色码相互转换

Khroma is the fastest way to discover, search, and save color combos you'll want to use.

Best Flat Colors For UI Design

Create color schemes with the color wheel or browse thousands of color combinations from the Color community.

提供渐变色和配色方案，还能从提供的图片中提取主要配色