I think you want to make do without materials. Anyhow, have a try on them and modify:


material mat_test
{ ambient_red = 255;
ambient_green = 255;
ambient_blue = 255;

diffuse_red = 0;
diffuse_green = 0;
diffuse_blue = 0;
specular_red=0;
specular_green=0;
specular_blue=0;
albedo=0;
power = 10;
}

ACTION leafaction
{
//...
my.material=mat_test;

}