Refactoring for Pete

Random.ino

// RandomColor.ino

struct RGB
{
  uint8_t r;
  uint8_t g;
  uint8_t b;
};

RGB palette[] PROGMEM =
{
  {128, 0,    0   },
  {0,   128,  0   },
  {0,   0,    128 },
  {255, 0,    0   },
  {0,   255,  0   },
  {0,   0,    255 }
};

uint16_t palette_count;

void setup() {
  Serial.begin(9600);
  randomSeed(analogRead(A0));
  palette_count = sizeof(palette) / sizeof(RGB);
}

void loop() {
  uint16_t rgb_index = random(0, palette_count);
  
  Serial.print(palette[rgb_index].r);
  Serial.print(", ");
  Serial.print(palette[rgb_index].g);
  Serial.print(", ");
  Serial.println(palette[rgb_index].b);
  
  delay(500);
}