After a foundation course at the St Albans School of Art, Brewster went on to specialise in fine art painting at Brighton Polytechnic in the early 70s, followed by a Postgraduate Printmaking Course. During this time, Brewster's primary tutor was the highly acclaimed Dennis Creffield (who in turn had been taught by David Bomberg) working with him in the life room and maintaining a keen interest in traditional oil painting techniques and focusing on expressionist and figurative expressionism working from landscape and still life. Gradually Brewster's interest moved more into abstract work based on a strong feeling for colour influenced by American, English and European Abstract artists, for example the St Ives School.
Brewster describes his style as essentially abstract expressionism but influenced and strongly inspired by the natural world, landscapes and seascapes, and poetic aspects such as light, shade and colour.
Over long periods of time, Brewster takes on certain themes, exploring the compositional possibilities that they present. He now works across different mediums although initially only working in oil generally on a large scale. In recent years, he uses acrylic much more combined with collage to build up the paint surface. Colour has become a key element in his work no longer relying on any specific motif, whilst developing compositional ideas, scale, paint handling and colour. As Brewster says, '...Colour has the ability to evoke emotions, create sensations and suggest feelings. The beauty and power of colour is central to images I make in much of my work and is an intrinsic part of the subject matter...'
To quote Professor Simon Olding in his monograph on the life and work of Martyn Brewster, in 1997:-
'If he is compelled to paint from nature, or driven by emotional circumstances to produce works of often passionate beauty using the force of abstract colour as a guiding principle, then it has proved to be a life's work of commanding strength and integrity.'