Help System (web edition)

The basic color system in Survo is CMYK (C=Cyan, M=Magenta, Y=Yellow,
K=blacK) with intensities of each color component from 0 to 1.
It is supported in PostScript.
For example, (0,0,0,0) is white and (1,1,1,0) or (0,0,0,1) is black.
(0,0,0,k) with 0<k<=1 is always safer for various shades of gray.
On the screen the RGB (R=Red, G=Green, B=Blue) system is used.
There is no unique correspondence between these two color systems.
More information e.g. from
http://dx.sheridan.com/advisor/cmyk_color.html 

Survo provides 3 different conversion rules selected by a RGB
specification.
By default (RGB=1), in screen graphics of Survo the CMYK colors are
converted to RGB by formulas
R=int(255*(1-min(1,C+K))),
G=int(255*(1-min(1,M+K))),
B=int(255*(1-min(1,Y+K))).

When Ghostscript is used for conversion of Survo PostScript files
to the PDF format, the colors are exactly the same on the screen
as the colors in GPLOT graphs created by this default setting (RGB=1).

Surprisingly a complete match has not attained when Adobe Distiller
is used for PS -> PDF conversion.

Approximate matching occurs by using either RGB=2 or RGB=3 in GPLOT.

For RGB=2 in GPLOT, the conversion formulas are
R=int(255*(1-C)*(1-K)),
G=int(255*(1-M)*(1-K)),
B=int(255*(1-Y)*(1-K))

and for RGB=3 (default before ver. 1.28 of SURVO MM) they are
R=int(255*(1-(C+K)/s),
G=int(255*(1-(M+K)/s),
B=int(255*(1-(Y+K)/s)
where s=min(1,K+max(C,M,Y).