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

As the titles says

code/modules/client/preferences.dm

@@ -51,6 +51,10 @@ datum/preferences
 	var/list/language_prefixes = list() //Kanguage prefix keys
 	var/list/gear						//Custom/fluff item loadout.
 	var/list/traits						//Traits which modifier characters for better or worse (mostly worse).
+	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
 
 		//Some faction information.
 	var/home_system = "Unset"           //System of birth.