Tektronix Z740/N - Phaser 740 Color Laser Printer Service Manual page 115

Single color mottled or with non-uniform
density streaks.
If a single color displays a mottled
appearance or if a single color shows many
vertical streaks of varying densities, then
that color's toner cartridge is running of
toner. Replace the cartridge.
104 Phaser 740 Color Printer