Blue and Yellow lights shining on performers, for example, produce the effect of white light except where one of the two colors is absent,as in the shadows. The shadow of one lamp, say the blue, is illuminated by the yellow lamp and appears yellow.
Not all colors are the result of the addition or subtraction of light. A clear cloudiness day time sky is blue because molecules in the air scatter blue light from the sun more ham they scatter red light. When we look towards the sun at sunset, we see red and orange colours because the blue light has been scatters out and away from the line of sight. The blueness is refracted