Daily Cycle For Loop Indexing

/*his sketch is still in beta.  The timing of he color changes must be set as well as the length of the daily cycle.*/
#include <FastLED.h>

#define dataPin 5
#define Color_Order GRB
#define CHIPSET WS2812B
#define NUM_LEDS 15
#define BRIGHTNESS 200

CRGB leds[NUM_LEDS];

DEFINE_GRADIENT_PALETTE(sunrise_gp) {
  0, 0, 0, 0,
  18, 98, 0, 0,
  56, 161, 83, 0,
  115, 212, 202, 0,
  179, 255, 253, 213,
  255, 255, 255, 255
};

CRGBPalette256 sunPal = sunrise_gp;
uint8_t paletteIndex = 0;
bool countUp = true;

void setup() {
  FastLED.addLeds<CHIPSET, dataPin, Color_Order>(leds, NUM_LEDS);
}

void loop() {
  EVERY_N_MILLISECONDS(100) {
    for (int i = 0; i < NUM_LEDS; i++) {
      leds[i] = ColorFromPalette(sunPal, paletteIndex);
    }

    FastLED.show();

    if (countUp) {
      paletteIndex += 1;
      if (paletteIndex == 255) {
        countUp = false;
      }
    } else {
      paletteIndex -= 1;
      if (paletteIndex == 0) {
        countUp = true;
      }
    }
  }
}