The color of a chemical is determined by its interaction with light. When light interacts with a substance, it can be absorbed, transmitted, or reflected. The color we perceive is the result of the light that is reflected back to our eyes.
If a chemical appears blue, for example, it means that it primarily reflects blue light and absorbs other wavelengths of light. In other words, the chemical absorbs light of certain wavelengths (such as red and green) and reflects predominantly blue light, which is then detected by our eyes.
Similarly, if a chemical appears red, it means that it reflects predominantly red light and absorbs other wavelengths. The same principle applies to other colors as well.
It's important to note that the color of a substance can be influenced by its molecular or atomic structure, as well as any pigments or dyes present. Different chemical compounds have different absorption and reflection properties, leading to variations in color.
In summary, the color of a chemical is determined by the wavelengths of light it absorbs and reflects.