Arduino UNO Ws2811 RGB problem

#include <FastSPI_LED2.h>
#define NUM_LEDS 2

CRGB leds[NUM_LEDS];

void setup() {
  LEDS.addLeds<WS2811, 11>(leds, NUM_LEDS, GRB);
}
void loop() {
//
//// This works as aspected, but green and red are not changed
//
//    LEDS.showColor(CRGB(0, 0, 10));
//    delay(1000);
//    LEDS.showColor(CRGB(0, 10, 0));
//    delay(1000);
//    LEDS.showColor(CRGB(10, 0, 0));
//    delay(1000);
//
//// This creates flickering on LED 2 and a blue/green on LED1
//
//      leds[0].g = 20;
//      leds[1].b = 20;
//      LEDS.show();
//
//// Same problem as firs one. (LEDs are green but should be red)
//
LEDS.showColor(CRGB::Red);
}