A rare Picasso painting on auction for the first time make its debut in Hong Kong at the start of a global tour on and is expected to fetch $50 million, auction house Sotheby's says. The painting -- "Femme au beret et a la robe quadrillee (Marie-Therese Walter)" -- is a colourful and angular depiction of Picasso's French lover with a dark silhouette looming behind her face.