How to mix the color Klein blue

Quick answer：

Klein blue, a deep, almost electric blue, is created by mixing phthalo blue with a small amount of ultramarine blue and white. Phthalo blue is a synthetic pigment with a high color saturation and intensity, while ultramarine blue is a natural pigment with a more muted, deeper tone. A little goes a long way when adding ultramarine blue to achieve the Klein blue effect.