"You need to wear jeans and a t-shirt on casual day.'

casual clothes are things like jeans and a t shirt nothing special u can get them any where

A casual black t - shirt

A brown casual show can go with a polo t shirt. This is because brown is considered one of the neutral colors, like white and black.

Casual shirts are shirts that are worn casually. These can be t shirts or sweat shirts. A shirt that is not considered to be casual and is considered to be more dressy is a polo or a button up collared shirt.