🧑‍💻 Add neo.set_background_color(rgbw)

Marlin/src/feature/leds/neopixel.cpp

 
 #ifdef NEOPIXEL_BKGD_INDEX_FIRST
 
-  void Marlin_NeoPixel::set_background_color(uint8_t r, uint8_t g, uint8_t b, uint8_t w) {
-    for  (int background_led = NEOPIXEL_BKGD_INDEX_FIRST; background_led <= NEOPIXEL_BKGD_INDEX_LAST; background_led++)
+  void Marlin_NeoPixel::set_background_color(const uint8_t r, const uint8_t g, const uint8_t b, const uint8_t w) {
+    for (int background_led = NEOPIXEL_BKGD_INDEX_FIRST; background_led <= NEOPIXEL_BKGD_INDEX_LAST; background_led++)
       set_pixel_color(background_led, adaneo1.Color(r, g, b, w));
   }
 
   void Marlin_NeoPixel::reset_background_color() {
     constexpr uint8_t background_color[4] = NEOPIXEL_BKGD_COLOR;
-    set_background_color(background_color[0], background_color[1], background_color[2], background_color[3]);
+    set_background_color(background_color);
   }
 
 #endif
   set_color(adaneo1.Color
     TERN(LED_USER_PRESET_STARTUP,
       (LED_USER_PRESET_RED, LED_USER_PRESET_GREEN, LED_USER_PRESET_BLUE, LED_USER_PRESET_WHITE),
-      (0, 0, 0, 0))
+      (255, 255, 255, 255))
   );
 }
 

Marlin/src/feature/leds/neopixel.h

   static void set_color(const uint32_t c);
 
   #ifdef NEOPIXEL_BKGD_INDEX_FIRST
-    static void set_background_color(uint8_t r, uint8_t g, uint8_t b, uint8_t w);
+    static void set_background_color(const uint8_t r, const uint8_t g, const uint8_t b, const uint8_t w);
+    static void set_background_color(const uint8_t (&rgbw)[4]) { set_background_color(rgbw[0], rgbw[1], rgbw[2], rgbw[3]); }
     static void reset_background_color();
   #endif