Gamblin Oil paints - Blue is the most commonly confused color in terms of its hue temperature. There is a widely held misconception that all blues are cool. This is not at all the case: Indanthrone, Cobalt, and Phthalo Blue, for example, are warm, and Ultramarine Blue is so warm that it’s almost purple. Since most greens in the natural world have a high degree of yellow in them, painters will appreciate the yellowy warmth of Phthalo Emerald while beautifully transparent Phthalo Green serves as the cooler or blue shade. Either Phthalo Green, completely lightfast with an extraordinary tinting strength, or Phthalo Emerald can be used to “boost” mineral colors in tints.