Lock key indicator with RGB matrix on QMK

keymap.c

// keymap setting and etc...

// store the state
static bool _is_key_locked = false;

void keyboard_post_init_user(void) {
  // need to stop effects and animations
  rgb_matrix_mode(RGB_MATRIX_NONE);
  rgb_matrix_sethsv(HSV_OFF);
}

void rgb_matrix_indicators_user(void) {
  int key_index = 10; // set your key index here
  if (_is_key_locked) {
    rgb_matrix_set_color(key_index, RGB_WHITE);
  } else {
    rgb_matrix_set_color(key_index, RGB_BLACK);
  }
}

bool process_record_user(uint16_t keycode, keyrecord_t *record) {
  switch (keycode) {
    case KC_A: // set your keycode here
      if (record->event.pressed) {
        _is_key_locked = !_is_key_locked;
      }
      break;
  }
  return true;
}

Thank you so much for share this!
I spent one day trying to figure out how to implement a function to change the color of just one key when pressed.
I was missing this bool var to control the event, trying to set the color inside the process_record_user().
Now it's working!!