When creating graphics, particularly for presentation or publication purposes, S does not always produce exactly that which is required. You can, however, customise almost every aspect of the display using graphics parameters. S maintains a list of a large number of graphics parameters which control things such as line style, colours, figure arrangement and text justification among many others. Every graphics parameter has a name (such as `col', which controls colours,) and a value (a colour number, for example.)
A separate list of graphics parameters is maintained for each active device, and each device has a default set of parameters when initialised. Graphics parameters can be set in two ways: either permanently, affecting all graphics functions which access the current device; or temporarily, affecting only a single graphics function call.