Why is Nitric acid often yellow in color?

Nitric acid:

1. Nitric acid is a chemical compound that has a chemical formula ${\mathrm{HNO}}_3$.
2. It is a mineral acid that's quite corrosive.

Color:

1. Nitric acid in its purest form is colorless.
2. When the heat is absorbed, it becomes extremely unstable.
3. Nitrogen dioxide (${\mathrm{NO}}_2$) is produced when Nitric acid is thermally decomposed.
4. As a result of the dissolution of Nitrogen dioxide, nitric acid turns yellow.

Hence, Nitric acid is often yellow in color.