The formula Mg(NH4)PO4 represents magnesium ammonium phosphate it is white in colour. K3[Co(NO2)6] is known as potassium hexanitritocobaltate(III). It is yellow in colour. The yellow colour is due to the presence of the cobalt ion (Co3+) in the complex, which absorbs certain wavelengths of light and reflects yellow light. MnO(OH)2is brown in colour. Fe4[Fe(CN)6]3 is blue in colour.
| Complex | Colour |
| Mg(NH4)PO4 | White |
| K3[Co(NO2)6] | Yellow |
| MnO(OH)2 | Brown |
| Fe4[Fe(CN)6]3 | Blue |