The document describes minimum ergonomic requirements and recommenations to be applied to colours assigned to text and graphic applications and images in which colours are discretely assigned. The specifications thus exclude photorealistic images and graphics. The document applies to both hardware and software for visual display terminals, because both these sources control the presentation and appearance of colour on the display screen. The specifications in this part of EN ISO 9241 are for images on computer displays that meet minimum requirements for users with normal colour vision. Displays conforming to this part will be suboptimal for persons with colour vision deficiencies. A lot of terms concerning displayed colours are defined.