RGB signal tower

https://youtu.be/4R88qWi_j-I

Perfect accesories for 3D printer with Marlin fw.
need to enable this feature in Configuration.h:

#define RGB_LED

and change pins for rgb led:

#if ENABLED(RGB_LED) || ENABLED(RGBW_LED)
#define RGB_LED_R_PIN 6
#define RGB_LED_G_PIN 4
#define RGB_LED_B_PIN 5
#define RGB_LED_W_PIN -1
#endif test

Next you can (but its not necessary) change in Marlin_main.cpp:

Red color in critical error or kill:

void kill(con