CSS color codes

Hex rgba gradient color codes

Discover — Art & Design Inspiration at ColRD.com
http://colrd.com/
Image color palette matching

spectrum.js Spectrum color picker
http://www.color-hex.com/

Convert it to its equivalent value in Hexadecimal, Binary, RGB, CMYK, HSL
http://www.colorhexa.com/

CSS color gradients
http://www.colorzilla.com/gradient-editor/