Opt for a dark green plaid long sleeve shirt and light blue ripped jeans if you're on a mission for an outfit idea for when you want to look casually cool. Dial down the casualness of your look by rounding off with brown leather desert boots. With the departure of snow come warmer afternoons and balmy nights and the need for a light and breezy ensemble just like this one. This getup proves that reaching your 30s is no reason to avoid casual clothing.