Apple Mac Performa 5300CD - Manual (Page 43)

Using the screen control buttons on your computer
You can adjust the level of light and dark on the screen of your built-in
monitor by using the screen control buttons on your computer (marked with
the ¸ icon).
m Press the button on the right to lighten your screen.
m Press the button on the left to darken your screen.
Screen control buttons ¸
33 Expanding Your Computer and Using Special Features