Adjective has 3 senses

• monochromatic(a = adj.pert) - of or relating to monochromatism;
Derived form noun monochromatism₁

• monochromatic(a = adj.all) homochromatic - (of light or other electromagnetic radiation) having only one wavelength; "monochromatic light"
Antonym: polychromatic

• monochromatic(s = adj.all) monochrome, monochromic, monochromous - having or appearing to have only one color;