The French artist Yves Klein's visual impact came from which color?

The French artist Yves Klein's first collective art exhibition was held at Blue Epoch at the gallery Appollinaise, Milan January,1957). He had featured there eleven identical blue canvases, using ultramarine pigment suspended in a synthetic resin Rhodopas. This was described by Klein as ''The Medium''.

He used to paint Madonna's robes in medieval paintings, using International Klein Blue or IKB 191,1962.This was a reminiscent of the lapis lazuli. In the Parisian exhibition, at the Irish Clert Gallery in May,1957, it was a seminal happening.To mark the opening,1001 blue balloons were released and blue cards were sent out using IKB stamps. In 1960, Klein deposited a Soleau envelope, registering the paint formula under the name of International Klein Blue.Yves Klein was born on 28th April,1928 and died on 6th June,1962. He was a leading member of Nouveau realisme, founded in 1960 by art critic Pierre Restany. In Blue Obelisk, a project failed to realise in 1958. But it was materiallized finally in 1983. Klein had appropriated the place de la Concorde by shining to the spotlights onto the central Obelisk.