diff --git a/global_defs.scad b/global_defs.scad
index c1756a8..9e67ba7 100644
--- a/global_defs.scad
+++ b/global_defs.scad
@@ -26,7 +26,7 @@
 //  Setting $bom after including lib overrides bom in the libs but not in the local file.
 //  Setting $_bom in the local file overrides it in the local file but not in the libs.
 //
-//function is_undef(x) = x == undef;
+rr_green = [0, 146/255, 0];                                               // RepRap logo colour
 
 $_bom           = is_undef($bom)             ? 0      : $bom;             // 0 no bom, 1 assemblies and stls, 2 vitamins as well
 $exploded       = is_undef($explode)         ? 0      : $explode;         // 1 for exploded view
@@ -34,7 +34,7 @@ layer_height    = is_undef($layer_height)    ? 0.25   : $layer_height;    // lay
 extrusion_width = is_undef($extrusion_width) ? 0.5    : $extrusion_width; // filament width when printing
 nozzle          = is_undef($nozzle)          ? 0.45   : $nozzle;          // 3D printer nozzle
 cnc_bit_r       = is_undef($cnc_bit_r)       ? 1.2    : $cnc_bit_r;       // minimum tool radius when milling 2D objects
-pp1_colour      = is_undef($pp1_colour)      ? [0, 146/255, 0] : $pp1_colour; // printed part colour 1, RepRap logo colour
+pp1_colour      = is_undef($pp1_colour)      ? rr_green : $pp1_colour;    // printed part colour 1, RepRap logo colour
 pp2_colour      = is_undef($pp2_colour)      ? "Crimson"  : $pp2_colour;  // printed part colour 2
 pp3_colour      = is_undef($pp3_colour)      ? "SteelBlue" : $pp3_colour; // printed part colour 3
 pp4_colour      = is_undef($pp4_colour)      ? "darkorange" : $pp4_colour;// printed part colour 4