Why did Pablo Picasso paint Guernica only in black and white?

Pablo Picasso painted Guernica using the grisaille technique, a method that employs a neutral, monochrome palette.1

By stripping the canvas of color, Picasso provided his abstracted forms and mythic symbolism with the stark immediacy and credibility of a newsreel or a newspaper article. This aesthetic choice effectively underscored the painting's role as an emotional response to the senseless violence of the Spanish Civil War and the carpet bombing of the Basque city, allowing the work to function as a universal symbol of the atrocities of war.21