"For more than 10 years, Matt Mullican has been continuously developing a sign system which is, on the one hand, a product of his imagination, and on the other, taken directly from everyday life. Signs as they can be found in airports, train stations, urban spaces - generally in all places where people of different origin and languages move about; signs for orientation that are as unambiguous as possible for everyone, indicating the way to the baggage reclaim, the telephone, the toilets, etc."
Mullican uses six colours, each assigned to one of the five levels, to illustrate these models:
Green designates the level of "elements". It is the lowest level and encompasses the realm of nature and the material characteristics of objects, the creation and development of which is not triggered or determined by mental processes.
Blue designates the "World Unframed", the field of unconscious, automatic activities taking place without reflection.
Yellow is the level of consciously-controlled processes of thought and action, through which the world is perceived, analysed and systematised.
Black and white are the colours of "language" as an abstract system of indication through which objects lose their individuality and are translated into pictures/signs.
Red designates the fifth and highest level, that of the "subjective", of mental activities determining our individual experience in relation to the signs.
In this manner, Mullican has also designed the model of an imaginary city, as an illustrated brochure of human knowledge and personal experience.