[R] Finding different hues for a mosaic plot compatible with grayscale printing

[Simon Kiss]

I'm working with the following code below to generate a
how do I set the h,c, and l values such that the significant, positive  
residuals appear different on a grayscale printer from significant  
grayscale residuals.  The challenge as I see it is that one can only  
distinguish the positive and negative residuals with the hue/. Varying  
the chroma and the luminance only affect the distinctions between  
large and small and significant and non significant.  But my positive  
and negative residuals are both large (absolutely) and significant,  
meaning that they will have the same chroma and luminosity, but  
different hues.
I guess the key here is to find two separate hue values that appear  
substantially different *on a grayscale printer* at the same chroma  
and luminance. I have read through Zeileis et al. (2007, 2008) but  
can't quite find the answer there.
I have also tried the Friendly shading to vary the line type, but I  
can't find line types that are different enough to communicate the  
difference between positive and negative residuals clearly.

Your assistance is appreciated.

 >mosaic(~educ+trade_off_scaled, shade=TRUE, main="Support For  
Environmental Protection At The Expense of Creating Jobs By  
Education", gp=shading_hcl(CST17$observed, CST17$expected, ASR17,  
df=6, h=c(260,0), c=c(100,0), l=c(90,0)),  
labeling_args=list(rot_labels=c(25,90,0,0), offset_labels=c(1,0,0,2),  
offset_varnames=c(2,0,0,4),  
set_varnames=c(trade_off_scaled="Protecting The Environment Is More  
Important Than Creating Jobs", educ="Level of Education")))

*********************************
Simon J. Kiss, PhD
SSHRC and DAAD Post-Doctoral Fellow
John F. Kennedy Institute of North America Studies
Free University of Berlin
Lansstraße 7-9
14195 Berlin, Germany
Cell: +49 (0)1525-300-2812,
Web: http://www.jfki.fu-berlin.de/index.html