This paper presents three rules for colouring of a Grant Chart that displays the machine and job schedules of a job shop. These rules have been used on the job schedules of a real job shop and the performance of the proposed rules has been measured with respect to four different data sets of the above job shop. Of the three rules the rule based on the jobs using the critical machines performed most satisfactorily according to the measure of performance used. This measure of performance is based on the principle of proper colouring according to which operations of the same job should receive the same colour, while neighbouring operations of a machine should receive different colours. The paper also proposed the concept of degree of neighbourliness which may form the basis for new heuristics for colouring.