Epson Stylus Pro 4000 Reference Manual page 146

Paper Configuration
The following settings in Paper Configuration let you make the
detailed paper settings.
Mode
Color Density
146
Printing with Mac OS 8.6 to 9.x
Description
Adjusts the strength of Color Density. Use a value in the
range of -50% to +50%. Drag the slider with your mouse to
the right direction (+) to deepen the color of your printout
or left direction (-) to lighten its color. You can also type
a number (-50 to +50) in the box next to the slider.
Use this function when you print on paper other than
Epson special media.
Set the scroll bar to the 0 position when you print on Epson
special media.
Note:
The color of printout cannot be deepened depends on
the printint mode.