#include <Adafruit_NeoPixel.h>

#define LED_PIN    20
#define ENABLE_PIN 19
#define NUM_LEDS   1

Adafruit_NeoPixel strip(NUM_LEDS, LED_PIN, NEO_GRB + NEO_KHZ800);

void setup() {
  pinMode(ENABLE_PIN, OUTPUT);
  digitalWrite(ENABLE_PIN, HIGH); 
  strip.begin();
  strip.show(); 
}

void loop() {

    strip.setPixelColor(0, strip.Color(255, 0, 0)); 
    strip.show();
    delay(100);
  
   
    strip.setPixelColor(0, strip.Color(0, 255, 0)); 
    strip.show();
    delay(100);
  
    // 蓝色
    strip.setPixelColor(0, strip.Color(0, 0, 255)); 
    strip.show();
    delay(100);

}

Upload the code and you can see the red, green and blue effects flashing alternately.