Using RGB color constants where appropiate

src/battle_anim_ghost.c

@@ -1005,7 +1005,7 @@ static void AnimTask_CurseStretchingBlackBg_Step1(u8 taskId)
         top = 0;
         bottom = 112;
         selectedPalettes = GetBattlePalettesMask(TRUE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE);
-        BeginNormalPaletteFade(selectedPalettes, 0, 16, 16, RGB(0, 0, 0));
+        BeginNormalPaletteFade(selectedPalettes, 0, 16, 16, RGB_BLACK);
         gTasks[taskId].func = AnimTask_CurseStretchingBlackBg_Step2;
     }