French to English Other Advertising / Public Relations Agricultural machinery

In this context, "carré" means the block of colour sitting behind the company name; a good example with be the logo of the company "Gap", with a square of dark blue and the text written in white on that background. What is the technical term for that in English?

Réservées aux annonces, les couleurs secondaires sont utilisées avec une opacité de 75% afin de conserver un effet de transparence au carré, en arrière-fond du logo.