--- a/vehicle.c
+++ b/vehicle.c
@@ -2041,11 +2041,21 @@
 }
 
 // XXX Temporary stub -- will be expanded
-PalSpriteID GetEngineColourMap(PlayerID player)
+static PalSpriteID GetEngineColourMap(PlayerID player)
 {
 	return SPRITE_PALETTE(PLAYER_SPRITE_COLOR(player));
 }
 
+PalSpriteID GetEnginePalette(EngineID engine_type, PlayerID player)
+{
+	return GetEngineColourMap(player);
+}
+
+PalSpriteID GetVehiclePalette(const Vehicle *v)
+{
+	return GetEngineColourMap(v->owner);
+}
+
 // Save and load of vehicles
 const SaveLoad _common_veh_desc[] = {
 	SLE_VAR(Vehicle,subtype,					SLE_UINT8),

--- a/vehicle.h
+++ b/vehicle.h
@@ -422,19 +422,20 @@
 
 #define INVALID_VEHICLE 0xFFFF
 
-// XXX Temporary interface -- will be expanded
-PalSpriteID GetEngineColourMap(PlayerID player);
+/**
+ * Get the colour map for an engine. This used for unbuilt engines in the user interface.
+ * @param engine_type ID of engine
+ * @param player ID of player
+ * @return A ready-to-use palette modifier
+ */
+PalSpriteID GetEnginePalette(EngineID engine_type, PlayerID player);
 
-static inline PalSpriteID GetEnginePalette(EngineID engine_type, PlayerID player)
-{
-	return GetEngineColourMap(player);
-}
-
-static inline PalSpriteID GetVehiclePalette(const Vehicle *v)
-{
-	return GetEngineColourMap(v->owner);
-}
-
+/**
+ * Get the colour map for a vehicle.
+ * @param v Vehicle to get colour map for
+ * @return A ready-to-use palette modifier
+ */
+PalSpriteID GetVehiclePalette(const Vehicle *v);
 
 /* A lot of code calls for the invalidation of the status bar, which is widget 5.
  * Best is to have a virtual value for it when it needs to change again */