A web page or site usually contains a theme made up of a set of CSS color properties that create a theme of colors. In summary, a theme is considered a set of styles worn by a website; these styles are the theme CSS properties. These themes are frequently created with individual CSS style sheets containing all the properties necessary to draw the theme. These theme style sheets can be swapped out on user setting preferences or actions, such as when they change to a light or dark mode with an available setting.