What blue did artist Yves Klein develop and use for many monochrome works after registering its paint process with France's INPI?

International Klein Blue

Yves Klein collaborated with a chemist to create this specific matte shade, which uses a unique synthetic resin to preserve the pigment's original intensity and brilliance. He famously used the color for his "Anthropometry" series, where he directed models to cover themselves in the paint and press their bodies against canvases.