His use of colour is devoid of any specific function, providing his paintings with a deep, material character.
Completely avoiding motifs, he rigorously aims at making colour the principal means of conveying a message.
On the basis of Minimal Art theories, Lerche considers colour rather than motif to be the main component in a painting.
His monochrome canvasses are often reworked several times, allowing the additional shades to play against the underlying tone.
In 1986, he decorated the ferry MS Niels Klim, performing his work as a total entity, from the top of ship to the bottom.