Zenith Z-100 PC series Service Manual page 265

Page
3.18
Circuit Description
,
\.
Bit 5 is only used in the 320 x 200 graphics submode to select the active
palette of screen display colors. If bit 5 is a logical 1, color is determined
by the logic of Table 3.6.
Table 3.S. Color Palette Number 1 Selection
C1
CO
COLOR
0 0
Defined by bits 0-3 of 1/0 port 3D9
0 1 Cyan
1
0
Magenta
White
If bit 5 is a logical 0, color is determined by the logic of Table 3.7.
Table 3.7. Color Palette Number 2 Selection
C1 CO COLOR
0
0
Defined by bits 0-3 of 1/0 port 3D9
0 1 Green
0 Red
1
Brown