Spanish antiques dealer and interior decorator Lorenzo Castillo appoints this residence in Madrid with his madcap mix of art and interiors. Enter and a sea of blue greets you, punctuated by the metallic green on a Koons-ian wall hanging. Move upstairs and the palette shifts to purple and red in the private rooms. Castillo’s trick for using this many hues in one color story? Echo patterns, such as the cube motif on the living room rug, carried through to the wallpaper in the upstairs bathroom.