Thanks for the replies! The FastLED works with no "ghost LEDs", but I still have some questions:
When changing leds[some_led_index].r, it actually changes the green value of the led. leds[some_led_index].g changes red. blue works normally. Is there anyone having same problems? Thanks.

This is the current settings I'm using:

#define M5_NEO_NUM 10
#define M5_NEO_PIN 15
CRGB leds[M5_NEO_NUM];
void setup()
  FastLED.addLeds<SK6812, M5_NEO_PIN>(leds, M5_NEO_NUM);
  // other setups...
}

Compiler complains that No hardware SPI pins defined. All SPI access will default to bitbanged output, so I also tried WS2811, but the same problem continues.

The revelant code:

void setLedSingleChannelValue(int led_no, String channel, int val) {
  Serial.println("led_no " + (String)led_no + ", channel " + channel + ", val " + (String)val);
  if (channel == "R") {
    if (led_no < 10) {
      leds[led_no].red = val;
    }
    else {
      if (led_no == 10 || led_no == 11) {
        for (int i = 0; i < 5; ++ i) {
          leds[i].red = val;
        }
      }
      if (led_no == 10 || led_no == 12) {
        for (int i = 5; i < 10; ++ i){
          leds[i].red = val;
        }
      }
    }
  }
  else if (channel == "G") {
    if (led_no < 10) {
      leds[led_no].g = val;
    }
    else {
      if (led_no == 10 || led_no == 11) {
        for (int i = 0; i < 5; ++ i) {
          leds[i].g = val;
        }
      }
      if (led_no == 10 || led_no == 12) {
        for (int i = 5; i < 10; ++ i){
          leds[i].g = val;
        }
      }
    }
  }
  else if (channel == "B") {
    if (led_no < 10) {
      leds[led_no].b = val;
    }
    else {
      if (led_no == 10 || led_no == 11) {
        for (int i = 0; i < 5; ++ i) {
          leds[i].b = val;
        }
      }
      if (led_no == 10 || led_no == 12) {
        for (int i = 5; i < 10; ++ i){
          leds[i].b = val;
        }
      }
    }
  }
  FastLED.show();
  delay(5);
}

void checkAndSetLedSingleChannel(int led_no, String channel, int delta) {
  int check_led_no = (led_no < 10) ? led_no : (led_no == 12) ? 9 : 0;
  int currentValue = getLedSingleChannelValue(check_led_no, channel);
  int afterValue = currentValue + delta;
  afterValue = (afterValue < 0) ? 0 : (afterValue > 255) ? 255 : afterValue;
  setLedSingleChannelValue(led_no, channel, afterValue);
}

void menu_setLedSingleChannel(int led_no, String channel) {
  ezMenu submenu(getLedHeaderText(led_no, "Set"));
  submenu.txtSmall();
  submenu.buttons("-1 # -10 # Back | OK # # +1 # +10 # -50 # +50 # ");
  submenu.addItem(channel + " | " + channel + "\t" + (String)getLedSingleChannelValue(led_no, channel));
  while(submenu.runOnce()) {
    String pickButton = submenu.pickButton();
    if (pickButton == "-1") {
      checkAndSetLedSingleChannel(led_no, channel, -1);
    }
    else if (pickButton == "+1") {
      checkAndSetLedSingleChannel(led_no, channel, 1);
    }
    else if (pickButton == "-10") {
      checkAndSetLedSingleChannel(led_no, channel, -10);
    }
    else if (pickButton == "+10") {
      checkAndSetLedSingleChannel(led_no, channel, 10);
    }
    else if (pickButton == "-50") {
      checkAndSetLedSingleChannel(led_no, channel, -50);
    }
    else if (pickButton == "+50") {
      checkAndSetLedSingleChannel(led_no, channel, 50);
    }
    submenu.setCaption(channel, channel + "\t" + (String)getLedSingleChannelValue(led_no, channel));
    delay(20);
  }
}

// The program enters from this function.
void menu_setLed(int led_no) {
  /*
  ez.msgBox("Set LED#" + (String)led_no, 
    "You have picked LED#" + (String)led_no);
  */
  ezMenu submenu(getLedHeaderText(led_no, "Set"));
  submenu.txtSmall();
  submenu.buttons("up # Back # Select # # down #");
  submenu.addItem("R | R\t" + (String)getLedSingleChannelValue(led_no, "R"));
  submenu.addItem("G | G\t" + (String)getLedSingleChannelValue(led_no, "G"));
  submenu.addItem("B | B\t" + (String)getLedSingleChannelValue(led_no, "B"));
  while(submenu.runOnce()) {
    String picked = submenu.pickName();
    if (picked == "black") {
    if (picked == "R" | picked == "G" || picked == "B") {
      menu_setLedSingleChannel(led_no, picked);
    }
    delay(20);
  }
}

Hello, I have just got my M5stack fire and is making a simple LED modifying program with M5ez. I use the same library as samples in arduino IDE, Adafuit_NeoPixel. The program compiles with no errors, but when I start to use, the LEDs behave wierd.

Here are the revalent code.

#define M5_NEO_NUM 10
#define M5_NEO_PIN 15

Adafruit_NeoPixel pixels = Adafruit_NeoPixel(M5_NEO_NUM, M5_NEO_PIN);

void setup() {
  #include <themes/default.h>
  #include <themes/dark.h>
  ezt::setDebug(INFO);
  pixels.begin();
  pixels.setBrightness(255);
  pixels.show();
  ez.begin();
}

Selecing which LED to control...

void mainmenu_leds() {
  ezMenu submenu("Set LED colors");
  submenu.txtSmall();
  submenu.buttons("up # Back # Select # # down #");
  for(int i = 0; i < 10; ++ i) {
    submenu.addItem("LED#" + (String)i);
  }
  submenu.upOnFirst("last|up");
  submenu.downOnLast("first|down");
  while (submenu.runOnce()) {
    int pickedItem = (int)submenu.pick() - 1;
    if (pickedItem >= 0 && pickedItem < 10) {
      menu_setLED(pickedItem);
    }
  }
}

Each LED gets individual control options here. (0 <= led_no <= 9)

void menu_setLED(int led_no) {
  /*
  ez.msgBox("Set LED#" + (String)led_no, 
    "You have picked LED#" + (String)led_no);
  */
  ezMenu submenu("Set LED#" + (String)led_no);
  submenu.txtSmall();
  submenu.buttons("up # Back # Select # # down #");
  //submenu.addItem("R | R\t0");
  //submenu.addItem("G | G\t0");
  //submenu.addItem("B | B\t0");
  submenu.addItem("black | Turn off");
  submenu.addItem("white | Turn bright");
  while(submenu.runOnce()) {
    if (submenu.pickName() == "black") {
      pixels.setPixelColor(led_no, pixels.Color(0, 0, 0));
      pixels.show();
      delay(20);
    }
    else if (submenu.pickName() == "white") {
      pixels.setPixelColor(led_no, pixels.Color(255, 255, 255));
      pixels.show();
      delay(20);
    }
  }
}

Expected behavior:
When "black" is picked, the corresponding LED should be turned off (pixels.Color(0,0,0))
When "white" is picked, the LED should turn white (pixels.Color(255,255,255))

What really happens:
Usually the corresponding LED behaves normally, but the other LED may also light up random color due to unknown reasons.
Also, when set LED#0 to black, it displays green. That means LED#0 cannot be turned off now.

I really don't know what is happening here, please help. Thanks in advance.