Adds in the option to color all synth parts and two sets of parts

As the titles says

code/modules/mob/living/carbon/human/human_defines.dm

@@ -23,6 +23,12 @@
 	var/g_skin = 0
 	var/b_skin = 0
 
+	//Synth colors
+	var/synth_color	= 0					//Lets normally uncolorable synth parts be colorable.
+	var/r_synth							//Used with synth_color to color synth parts that normaly can't be colored.
+	var/g_synth							//Same as above
+	var/b_synth							//Same as above
+
 	var/size_multiplier = 1 //multiplier for the mob's icon size
 	var/damage_multiplier = 1 //multiplies melee combat damage
 	var/icon_update = 1 //whether icon updating shall take place