By the time he painted this picture Mondrian had further developed his ideas and formulated them as a set of principles governing his painting which he wrote down in 1926. These principles maybe summarised as: only primary colours and the non-colours, black and white; only straight lines and only in vertical or horizontal configuration; only squares and rectangles. Further, there must be no spatial illusion - the painting must appear absolutely flat, and all the elements must be in a balanced relationship, in equilibrium, although, equally, there must be no symmetry. From this it can be seen that in general Mondrian's painting represented the ultimate development up to that time of the idea of pure painting - the basic ingredients of painting, line, form and colour, used only in their most elementary, irreducible forms. For Mondrian a central meaning of his painting was embodied in the crossing of lines at right angles: paragraph four of General Principles of Neo-Plasticism states 'Abiding equilibrium is achieved through opposition and is expressed by the straight line ... in its principal opposition i.e. the right angle'. This basic crossing of lines represented for Mondrian the union of all opposites, masculine/feminine, positive/negative, into a universal expression of harmony and unity. He wrote 'The positive and the negative break up oneness, they are the cause of all unhappiness. The union of the positive and negative is happiness.' Mondrian also saw Neo-Plasticism as the vehicle for expression of an ideal vision of society. Under the heading Psychological and Social Consequences of Neo-Plasticism he wrote 'Neo-Plasticism ... stands for equity, because the equivalence of the plastic means in the composition demonstrates that it is possible for each, despite differences, to have the same value as others.' By this Mondrian meant that each coloured rectangular element (the 'plastic means'), although different from all the others, plays an equal role in the composition. Thus, his paintings could represent a state of society in which people were different but equal.
Towards the end of the 1930s Mondrian came to feel that his early Neo-Plastic paintings were too static, lacking the feeling of life. In 'Composition with Red, Yellow and Blue' painted from 1937-42 [Tate Gallery T00648], he uses irregularly spaced thick black lines to set up a distinctive optical rhythm, and small areas of pure primary colour (his earlier colours were muted with grey) that also activate the picture. This tendency reached its fullest development in Mondrian's last years, spent in New York City, where 'Composition with Red, Yellow and Blue' was completed and where he began to give his pictures titles such as 'Broadway Boogie-Woogie', relating to the City and to jazz music. In an interview given in New York. Mondrian said that what he now wanted was to express 'dynamic movement in equilibrium.'
Simon Wilson, Tate Gallery: An Illustrated Companion, Tate Gallery, London, revised edition 1991, p.144