QMS 2425 Reference page 160

The term "pen" in the HP-GL emulation refers to a logical pen (in
other words, the current pen position) rather than to a physical pen on
a plotter. A pen and a pen color are selected to draw images. This
emulation supports 8 pens and pen colors.
Since your QMS 2425/2425 TURBO Print System is a monochrome
(black and white) printer, the pen colors are converted to shades of
gray. The default color mappings for the 8 pens are as follows:
Pen
1
2
3
4
5
6
7
8
» Note: The default color for both pen 1 and pen 2 is black. However,
the pen width for these two pens is different. Pen 1 is 0.7 mm and pen
2 is 0.3 mm.
The printer maps each pen to its assigned color, then converts the
color to a grayscale using the National Television System Committee
(NTSC) standard equation for encoding color. This equation converts
a given set of CMYK values to grayscale. For the 8 pen colors
assigned to pens 1 - 8, the printer uses the designated grayscale; for
any other pen color, the printer uses the following equation:
[(C*0.3) + (M*0.59) + (Y*0.11) + K]
Note: This equation assumes that each grayscale is a byte value that
»
ranges from 0 to 255 (100%). If the sum of the left-side (calculation in
brackets) of the NTSC equation is greater than 255, then the sum is
set equal to 255.
Pen Color
Black
Black
Red
Green
Blue
Violet
Orange
Brown
Level of Gray
100%
100%
70%
41%
89%
59%
25.8%
50%
255