Facebook brand color is blue.
Hex, RGB, CMYK and Pantone® (PMS) color codes and values are listed below. You can also download the color palette of the Facebook brand with their hexadecimal codes.
Unless stated, all the colors are from the official Facebook brand guidelines, a link to which is provided on this page along with a link to their web site.
Please note: Typically, hex and RGB color codes are for digital use and CMYK values are for standard color printers.