The ability to distinguish colours, either implicitly or explicitly, is a standard requirement for acceptance into certain professions and occupations, eg airline pilot, train driver. Whether or not an individual with defective colour vision is capable of carrying out a particular occupation satisfactorily depends on the defect and the importance of accurate colour discrimination in the task to hand. Examples of current restrictions to employment within certain professions and occupations are detailed in the AOP Handbook (Association of Optometrists 2001). Many employers are currently reassessing their policy on the use of colour defectives in the light of the Disability Discrimination Act (1995).