#include "FastLED.h"

CRGB leds[600];

void setup()
{
  FastLED.addLeds<WS2812B, 10, GRB>(leds, 600);
  FastLED.setBrightness(255);
}

int hue = 0;
int huesteps = 0;

void loop()
{ 
  int l = random16(600);
  leds[l] = CHSV(hue, 128 + random8(128), 255);
  l = random16(600);
  leds[l] = CRGB::Black;
  l = random16(600);
  leds[l] = CRGB::Black;

  huesteps++;
  if(huesteps == 100)
  {
    huesteps = 0;
    hue = (hue + 1) % 256;
  }

  FastLED.show();
}