Congrats on an excellent tool Dr Rorden.

I'm trying to overlay an edge file with negative and positive values and assigning blue and red colors respectively to each population.

It works in some LUT's but only using different colors, not pure blue and red, for example, selecting all nodes regardless of polarity gl.nodepolarity(0) : 

import gl
gl.resetdefaults()
gl.meshload('brain.mz3')
gl.edgeload('All.edge')
gl.nodesize(3,1)
gl.nodethresh(0,4)
gl.nodecolor('GE', 1)
gl.edgesize(1.5,1)
gl.nodepolarity(0)
gl.edgethresh(0.0,0.6)
gl.edgecolor('Yellow [r+g]',0)
gl.shaderxray(65,0.8)
gl.shadername('Metal')
gl.shaderforbackgroundonly(1)
gl.viewaxial(1)

This works but with the wrong colors.

Trying to load the node/edge file twice (as a copy) with separate calls in between to gl.nodepolarity(-1), gl.edgecolor('Blue]',0) and then gl.nodepolarity(1), gl.edgecolor('Red]',0) and finally showing them all gl.nodepolarity(0) also does not work.

Is this at all possible? Many thanks for any pointers,

Neil