blinking external led with psu

technically works, but blinking incorrectly

sketch_may4b_nerdtutorialscp/sketch_may4b_nerdtutorialscp.ino

@@ -0,0 +1,20 @@
+#include <FastLED.h>
+
+#define LED_PIN     15
+#define NUM_LEDS    5
+
+CRGB leds[NUM_LEDS];
+
+void setup() {
+
+  FastLED.addLeds<WS2812, LED_PIN, GRB>(leds, NUM_LEDS);
+  
+}
+
+void loop() {
+  
+  leds[0] = CRGB(255, 0, 0);
+  FastLED.show();
+  delay(500);  
+  leds[1] = CRGB(0, 255, 0);
+}