See how you like this - http://www.ogre.nu/source/tufte.inc ;
I use it in the top two images in http://www.ogre.nu/doodle.html
Tufte recommends unsaturated colors; hence my name for the pigment.
The slope vectors are chosen so that luminance is roughly constant
for a given value of slope y.
--
Anton Sherwood, http://www.ogre.nu/
