Merleau-Ponty is talking about the experiments with color perception which show, that the color is felt, and the bodily attitude of meeting that particular color is adopted, before we are cognitively aware of seeing the colour (among other things):
“The motor significance of colours is comprehensible only if they cease to be closed states or indescribable qualities presented to an observing and thinking subject, and if they impinge within me upon a certain general setting through which I come to terms with the world; if, moreover, they suggest to me a new manner of evaluating, and yet if motility ceases to be the mere consciousness of my movements from place to place in the present or immediate future, and becomes the function which constantly lays down my standards of size and the varying scope of my being in the word. Blue is that which prompts me to look in a certain way, that which allows my gaze to run over in a specific manner. It is a certain field or atmosphere presented to the power of my eyes and of my whole body. Here the experience of colour confirms and elucidates the correlations established by inductive psychology. Green is commonly regarded as a “restful” colour. ‘It encloses me within myself and brings a peaceful state,’ says one patient. (Goldstein and Rosenthal, Zum Problem der Wirkung der Farben auf den Organismus, p.23) It ‘makes no demands on us and does not enjoin us to do anything,’ says Kandinsky. Blue seems to ‘yield to our gaze,’ says Goethe. On the other hand, he adds, red ‘invades the eye.’ (Kandinsky, Form und Farbe in der Malerei; Goethe, Farbenlehre, in particular Abs. 293; quoted by Goldstein and Rosenthal. Ibid.) Red has a ‘rending’, and yellow a ‘stinging’ effect, says one of Goldstein’s patients. Generally speaking we have on the one hand, with red and yellow, ‘an experience of being torn away, of a movement away from the centre’; on the other hand, with blue and green, that of ‘repose and concentration’. (Goldstein and Rosenthal, pp 23-5) We can reveal the soporific and motor basis of qualities, or their visual significance, by employing stimuli which are either weak or of short duration. In this case the colour, before being seen, gives itself away through the experience of a certain bodily attitude appropriate only to that colour and precisely indicative if it; ‘there is in my body a sensation of slipping downwards, so that it cannot be green, and can only be blue but in fact I see no blue’, (Werner, Untersuchungen über Empfindung ind Empfinden, I, p.158) says one subject. Another says: ‘I clenched my teeth, and so I know that it is yellow.’ (Ibid.) If a light stimulus is gradually increased from a subliminal intensity, there is first of all the experience of a certain bodily disposition and suddenly the sensation runs into and ‘spreads through the visual domain’. (Ibid., p.159) Just as, when I look closely at snow, I break its apparent “whiteness’ up into a world of reflections and transparencies, so within a musical note a ‘micro melody’ can be picked out and the interval heard is merely the final patterning of a certain tension felt throughout the body. (Werner, Über die Ausprägung von Tongestalten)
The representation of a colour in subjects who have lost it is made possible by displaying before them any real colours whatsoever. The real colour produces in the subject a ‘concentration of colour experience’ which enables him to ‘draw together the colours in his eye’. (Werner, Untersuchungen über Empfindung ind Empfinden, I, p.160) Thus, before becoming an objective spectacle, quality is revealed by a type of behaviour which is directed towards it in its essence, and this is why my body no sooner adopted the attitude of blue than I am vouchsafed a quasi-presence of blue. We must therefore stop wondering how and why red signifies effort or violence, green restfulness and peace; we must rediscover how to live these colours as our body does, that is, as peace or violence in a concrete form. When we say that red increases the compass of our reactions, we are not to be understood as having in mind two distinct facts, a sensation of redness and motor reactions – we must be understood as meaning that red, by its texture as followed and adhered to by our gaze, is already the amplification of our motor being. The subject of sensation is neither the thinker who takes note of a quality, not an inert setting which is affected or changed by it, it is a power which is born into, and simultaneously with, a certain existential environment, or is synchronized with it. The relations of sentient to sensible are comparable with those of the sleeper to his slumber: sleep comes when a certain voluntary attitude suddenly receives from outside the confirmation for which is has been waiting. I am breathing deeply and slowly in order to summon sleep, and suddenly it is as if my were connected to some great lung outside myself which alternately calls forth and forces back my breath. A certain rhythm of respiration, which a moment ago I voluntarily maintained, now becomes my very being, and sleep, until now aimed at as a significance, suddenly becomes a situation. In the same way I give an ear, or look, in the expectation of sensation, and suddenly the sensible takes possession of my ear or my gaze, and I surrender a part of my body, even my whole body, to this particular manner of vibrating and filling space known as blue or red.” (PhP 210-212)
It is very important in this passage to see Merleau-Ponty’s refusal to take both the rationalist interpretation of perception, in which the “subject of perception” would be seen as “a thinker who takes note of a quality”, and the empiricist interpretation or a tabula rasa, “an inert setting” affected by a sensation, and instead stresses the phenomenological take on a human being, who is always already in touch with what is felt, before even being aware of it, and, a uniquely Merleau-Pontian phenomenological take, when that being in touch happens when bodies meet bodies, when here not just the eye meets the red, but the whole body reverberates to, with, and according to the red that it meets.