Which of the following is not a chromophore?

$-{\mathrm{NH}}_2$ group is not a chromophore but is an auxochrome

Chromophore is that part of the molecule which when exposed to visible light will absorb and reflect a certain color. Auxochrome is a group of atoms which is functional and has the capability to alter the capacity of the chromophore to reflect colors. Azobenzene is an example of a dye which contains a chromophore. 

Examples of auxochrome groups are -COOH,-SO₃H, -OH, and -NH₃.