The exposition is radically changed to embrace colour in its dimension of transparency and translucency, suggesting experiments which can be performed particularly in etching, but also those more relevant to a judgement than to an experience, more strongly radical dealing with the possible origin of colour in the eye and even those leaving no external tangible traces whatsoever but which nonetheless are deeply illuminating and even have profound but paradoxical effects on one's subsequent colour sensitivity.
Colour is determined by what occupies the visual field and its changes under different lights but it also originates in quite another way inside the eye itself and by its complex mechanism. Is it the interacting between these two which generates colours as seen? For instance the presence of a red object provokes a green after-image in its surroudings and even in the case of a non-coloured object there is tendency to see it as warmish or coldish, as tending towards reddish or bluish. We might question whether colour is an outside stimulus or if it originates in the eye itself.

Exploring this second source of colour sensations - how they arise within the eye itself - how colours can be simply managed mechanically by exerting a mild amount of pressure on the closed eyes with the fingers and how one can enjoy the panoply of pure colours which arise. This is logically different from seing an external object's colour. It is both visual and visionary. It is not exactly "seeing" but a sensation between seeing and having a slight pain. Such an experiment is done by few artists who fear injury to the eye, rather it is imagined simply, but it is complex, the visionary colours changing slowly, overlaying each other with imaginable richness.
The flux of colours thus provoked can change slowly - at their own rates overlapping, separating, fading slowly or rapidly - all transparent so their overlappings can be registered. This is an experiment or experience without tangible traces - only one's intrinsic sense of colour possibilities is vastly enlarged.

(Fascinated by how this comes about, S.W. Hayter wanted to explore the eye's mechanisms and began to converse with leading neuro-scientists both in Europe and in America making notes for a projected book. Although the book remained unfinished or only notes, the subject matter stuck in his mind and his considerations. This might have been a source of the colour sense in his last paintings which were subtly vivid, trembling, wherein he accepted optical illusions as visual realities and was a source of his penetrating but obscure remarks exchanged with his collegues.)

Experimental Plate

Coloured Chords

After-Image (Vibrations)

The Lie of Color (Pulsations)