Hello,

The colors are visible because of the different ranges of wavelengths. In the light spectrum, the part which covers visible light can be roughly broken into 7 parts i.e. Violet, Blue, Indigo, Green, Yellow, Orange, and Red. But human eye is capable of differentiating even combinations of these colours, which results in formation of new contrasting colours.

The human eye can see more than 7,000,000 colors.

Hope this Helps