Red, green and orange on a bicolor matrix, on an Arduino Uno

// A red and green 8x8 matrix: eight rows from the Uno, sixteen columns from
// two chained 74HC595s.
//
//   rows R1..R8 (the anodes)       -> pins 2 to 9
//   74HC595 DS 11, SH_CP 13, ST_CP 12; the first chip's Q7S into the second's DS
//   first 595 Q0..Q7  -> red columns RC1..RC8, each through 1k
//   second 595 Q0..Q7 -> green columns GC1..GC8, each through 1k
//
// A column's LED lights when its row is HIGH and its column output LOW, so the
// column bytes are sent inverted. One row is on at a time; red and green
// together make orange.

const uint8_t ROW_PINS[8] = {2, 3, 4, 5, 6, 7, 8, 9};
const uint8_t DATA = 11, LATCH = 12, CLOCK = 13;

const uint8_t FACE[8] = {0x3C, 0x42, 0xA5, 0x81, 0xA5, 0x99, 0x42, 0x3C};

void columns(uint8_t red, uint8_t green) {
  digitalWrite(LATCH, LOW);
  shiftOut(DATA, CLOCK, MSBFIRST, (uint8_t)~green);  // ends up in the second chip
  shiftOut(DATA, CLOCK, MSBFIRST, (uint8_t)~red);
  digitalWrite(LATCH, HIGH);
}

void drawFor(bool red, bool green, unsigned long ms) {
  unsigned long start = millis();
  while (millis() - start < ms) {
    for (uint8_t r = 0; r < 8; r++) {
      // Q0 is column 1, so the leftmost dot is bit 0: reverse the row's bits.
      uint8_t row = 0;
      for (uint8_t b = 0; b < 8; b++) row |= ((FACE[r] >> b) & 1) << (7 - b);
      columns(red ? row : 0, green ? row : 0);
      digitalWrite(ROW_PINS[r], HIGH);
      delay(2);
      digitalWrite(ROW_PINS[r], LOW);
    }
  }
}

void setup() {
  for (uint8_t i = 0; i < 8; i++) pinMode(ROW_PINS[i], OUTPUT);
  pinMode(DATA, OUTPUT);
  pinMode(LATCH, OUTPUT);
  pinMode(CLOCK, OUTPUT);
}

void loop() {
  drawFor(false, true, 600);  // green
  drawFor(true, true, 600);   // orange
  drawFor(true, false, 600);  // red
  delay(300);                 // dark, then green again
}