It had already become clear to Goethe in Italy that all colour-experience is based on a polarity, which he found expressed by painters as the contrast between 'cold' and 'warm' colours. Now that the coming-into-being of the blue of the sky and of the yellow of the sun had shown themselves to him as two processes of opposite character, he recognized in them the objective reason why both colours are subjectively experienced by us as opposites. 'Blue is illumined darkness - yellow is darkened light' - thus could he assert the urphenomenon, while he expressed the relation to Light of colours in their totality by saying: 'Colours are Deeds and Sufferings of Light.'