In the catalogue for his 1963 exhibition, Heron wrote of his paintings from 1962: 'Painting has another continent left to explore, in the direction of colour (and in no other direction). Painting, like science, cannot discover the same things twice over: it is therefore compelled in those directions which the still undiscovered and the unexplored dictate. It seems obvious to me that we are still only at the beginning of our discovery and enjoyment of the superbly exciting facts of the world of colour. One reels at the colour possibilities now: the varied and contrasting intensities, opacities, transparencies; the seeming density and weight, warmth, coolness, vibrancy; or the superbly inert "dull" colours - such as the marvellously uneventful expanses of the surface of an old green door in the sunlight. Or the terrific zing of a vibrant vibration ... a violent violet flower, with five petals, suspended against the receptive furry green of leaves in a greenhouse! Violent violet cobalt! Certainly I can get a tremendous thrill from suddenly seeing two colours juxtaposed - anywhere, indoors or out (but I am no landscape painter in disguise, incidentally)'.