Brown nails design becomes one of the most popular Fall nail colors trends 2021. Brown is a combination of multiple colors, similar to wood, coffee, chocolate, etc. From darker colors to lighter colors, there are few shades of brown. It is a composite color composed of red, yellow, and blue. This color exists in many things in nature, such as hazelnuts, cocoa, wood, soil, human and animal hair color, etc. Brown nails are the most popular because they look natural and fit almost any shape of nails.