diff --git a/examples/demo.png b/examples/demo.png
index eca95ed..1197497 100644
Binary files a/examples/demo.png and b/examples/demo.png differ
diff --git a/examples/demo.scad b/examples/demo.scad
index 04368b6..2a14860 100644
--- a/examples/demo.scad
+++ b/examples/demo.scad
@@ -1,28 +1,63 @@
 include <../gears.scad>
+
+// Toggle to render the demo with per-gear colors for easier PNG lookup.
+show_colors = true;
+
+// Color palette by gear type (high-contrast, distinct).
+COLOR_PLANETARY = [0.90, 0.15, 0.15];
+COLOR_RACK = [0.10, 0.55, 0.95];
+COLOR_MOUNTABLE_RACK = [0.10, 0.70, 0.55];
+COLOR_HERRINGBONE_RACK = [0.80, 0.45, 0.10];
+COLOR_SPUR = [0.60, 0.15, 0.75];
+COLOR_RACK_AND_PINION = [0.90, 0.75, 0.10];
+COLOR_BEVEL = [0.15, 0.75, 0.25];
+COLOR_BEVEL_HERRINGBONE = [0.55, 0.45, 0.10];
+COLOR_WORM = [0.10, 0.65, 0.65];
+COLOR_WORM_GEAR = [0.95, 0.40, 0.70];
+
+// Legend (gear_type => color)
+// planetary_gear => COLOR_PLANETARY
+// rack => COLOR_RACK
+// mountable_rack => COLOR_MOUNTABLE_RACK
+// herringbone_rack => COLOR_HERRINGBONE_RACK
+// spur_gear => COLOR_SPUR
+// rack_and_pinion => COLOR_RACK_AND_PINION
+// bevel_gear => COLOR_BEVEL
+// bevel_herringbone_gear => COLOR_BEVEL_HERRINGBONE
+// worm => COLOR_WORM
+// worm_gear => COLOR_WORM_GEAR
+
+// planetary_gear
+color(show_colors ? COLOR_PLANETARY : undef)
 planetary_gear(modul=1, sun_teeth=30, planet_teeth=60, number_planets=3,
                width=5, rim_width=3, bore=3, pressure_angle=20);
 
 translate([0,-85,0])
+color(show_colors ? COLOR_RACK : undef)
 rack(modul=1, length=60, height=5, width=20, pressure_angle=20, helix_angle=0);
 
 translate([50,-85,0])
 rotate([0,0,20])
+color(show_colors ? COLOR_MOUNTABLE_RACK : undef)
 mountable_rack(modul=1, length=60, height=5, width=20, pressure_angle=20, helix_angle=0, profile=3, head="PH",fastners=3);
 
 translate([-50,-85,5])
 rotate([0,0,-60])
 rotate([90,0,0])
+color(show_colors ? COLOR_HERRINGBONE_RACK : undef)
 herringbone_rack(modul=1, length=60, height=5, width=20, pressure_angle=20, helix_angle=45);
 
 //mountable_herringbone_rack(modul=1, length=60, height=5, width=20, pressure_angle=20, helix_angle=45, profile=3, head="PH",fastners=3);
 
 translate([-85,-50,0])
+color(show_colors ? COLOR_SPUR : undef)
 spur_gear (modul=1, tooth_number=30, width=5, bore=4, pressure_angle=20, helix_angle=20, optimized=true);
 
 //herringbone_gear (modul=1, tooth_number=30, width=5, bore=4, pressure_angle=20, helix_angle=30, optimized=true);
 
 translate([95,-50,0])
 rotate([0,0,20])
+color(show_colors ? COLOR_RACK_AND_PINION : undef)
 rack_and_pinion (modul=1, rack_length=50, gear_teeth=30, rack_height=4, gear_bore=4, width=5, pressure_angle=20, helix_angle=0, together_built=true, optimized=true);
 
 //ring_gear (modul=1, tooth_number=30, width=5, rim_width=3, pressure_angle=20, helix_angle=20);
@@ -34,9 +69,11 @@ rack_and_pinion (modul=1, rack_length=50, gear_teeth=30, rack_height=4, gear_bor
 //planetary_gear(modul=2, sun_teeth=16, planet_teeth=9, number_planets=5, width=5, rim_width=3, bore=4, pressure_angle=20, helix_angle=30, together_built=true, optimized=false);
 
 translate([30,-48,0])
+color(show_colors ? COLOR_BEVEL : undef)
 bevel_gear(modul=1, tooth_number=30,  partial_cone_angle=45, tooth_width=5, bore=4, pressure_angle=20, helix_angle=20);
 
 translate([-52,0,0])
+color(show_colors ? COLOR_BEVEL_HERRINGBONE : undef)
 bevel_herringbone_gear(modul=1, tooth_number=30, partial_cone_angle=45, tooth_width=5, bore=4, pressure_angle=20, helix_angle=30);
 
 //bevel_gear_pair(modul=1, gear_teeth=30, pinion_teeth=11, axis_angle=100, tooth_width=5, gear_bore=4, pinion_bore=4, pressure_angle = 20, helix_angle=20, together_built=true);
@@ -56,8 +93,10 @@ bevel_herringbone_gear_pair(
 */
 
 translate([92,0,0])
+color(show_colors ? COLOR_WORM : undef)
 worm(modul=1, thread_starts=2, length=15, bore=4, pressure_angle=20, lead_angle=10, together_built=true);
 
 translate([120,20,0])
 rotate([0,0,-20])
+color(show_colors ? COLOR_WORM_GEAR : undef)
 worm_gear(modul=1, tooth_number=30, thread_starts=2, width=8, length=20, worm_bore=4, gear_bore=4, pressure_angle=20, lead_angle=10, optimized=1, together_built=1, show_spur=1, show_worm=1);