cycle through colors on an RGB LED

sketch.c

int red = 11;
int green = 10;
int blue = 9;

long spectrum[] = {
  0xff0000, // 0 red
  0xffa500, // 1 orange
  0xffff00, // 2 yellow
  0x00ff00, // 3 green
  0x0000ff, // 4 blue
  0x4b0082, // 5 indigo
  0x9400d3, // 6 dark violet
};
int colors = 7;

int redAmount = 255;
int greenAmount = 0;
int blueAmount = 0;

int nextColor = 1;

int stepsSinceLastSwitch = 0;

void setup() {
  // put your setup code here, to run once:

  pinMode(red, OUTPUT);
  pinMode(green, OUTPUT);
  pinMode(blue, OUTPUT);
  Serial.begin(9600);
}

void RGB_color(int red_value, int green_value, int blue_value)
{
  analogWrite(red, red_value);
  analogWrite(green, green_value);
  analogWrite(blue, blue_value);
//  Serial.print(redAmount);
//  Serial.print(" red, ");
//  Serial.print(greenAmount);
//  Serial.print(" green, ");
//  Serial.print(blueAmount);
//  Serial.println(" blue");

}

void loop() {
  // put your main code here, to run repeatedly:
  RGB_color(redAmount, greenAmount, blueAmount);

  int nextRed   = (spectrum[nextColor]&0xff0000) >> 16;
  int nextGreen = (spectrum[nextColor]&0x00ff00) >>  8;
  int nextBlue  = (spectrum[nextColor]&0x0000ff);

  int dR = nextRed - redAmount;
  int dG = nextGreen - greenAmount;
  int dB = nextBlue - blueAmount;

  if (dR == 0 && dG == 0 && dB == 0) {
    nextColor = (nextColor + 1) % 7;
    Serial.print("after ");
    Serial.print(stepsSinceLastSwitch);
    Serial.print(" steps, next color will be ");
    Serial.println(nextColor);
    stepsSinceLastSwitch = 0;
    delay(250);
    return;
  }

  stepsSinceLastSwitch += 1;

  int aR = abs(dR);
  int aG = abs(dG);
  int aB = abs(dB);

  int steps = 0;

  if (aR > 0 && (aR < aG || aG == 0) && (aR < aB || aB == 0)) {
    steps = aR;
  } else if (aG > 0 && (aG < aB || aB == 0)) {
    steps = aG;
  } else {
    steps = aB;
  }
  if (steps == 0) {
    // this shouldn't happen?
    Serial.println("BOOOM!");
    redAmount = 0;
    greenAmount = 0;
    blueAmount = 0;
    return;
  }
  if (steps > 50) {
    steps /= 4;
  }

  redAmount = takestep(redAmount, dR, steps);
  greenAmount = takestep(greenAmount, dG, steps);
  blueAmount = takestep(blueAmount, dB, steps);

  delay(20);
}

int takestep(int val, int d, int steps) {
  if (d == 0) {
    return val;
  }
  return val + (d / steps);
}