Cobalt compounds exhibit a wide range of colors, thanks to the variable oxidation states and coordination complexes that cobalt can form. Here are some common examples:

Cobalt(II) compounds:

* Pink: Cobalt(II) chloride (CoCl₂), cobalt(II) sulfate (CoSO₄)

* Blue: Cobalt(II) nitrate (Co(NO₃)₂)

* Green: Cobalt(II) carbonate (CoCO₃)

* Purple: Cobalt(II) ammonium sulfate (Co(NH₄)₂(SO₄)₂)

Cobalt(III) compounds:

* Yellow: Potassium hexacyanocobaltate(III) (K₃[Co(CN)₆])

* Red: Cobalt(III) acetate (Co(CH₃COO)₃)

* Orange: Cobalt(III) chloride (CoCl₃)

Other colors:

* Black: Cobalt(II) oxide (CoO)

* Brown: Cobalt(II) hydroxide (Co(OH)₂)

It's important to note that the color of a cobalt compound can be affected by factors such as:

* Oxidation state of cobalt: Cobalt(II) compounds are typically pink or blue, while cobalt(III) compounds can be yellow, red, or orange.

* Ligands: The ligands coordinated to the cobalt ion can significantly influence the color of the compound.

* Solvent: The solvent in which the compound is dissolved can also affect its color.

The colors of cobalt compounds are often used in pigments, ceramics, and glassmaking.