This scenario presents how to handle the brightness control of the tri-coloured LEDs. Both LEDs are electrically bound and cannot be controlled independently. Those LEDs have 3 colour channels, controlled independently: R (Red), G (Green) and B (Blue). Mixing of those colours creates other ones, such as pink and violet. Each R G B channel can be controlled with a separate GPIO to switch it on or off or control brightness using a PWM signal, as presented in this tutorial.

define the necessary pins and functions:

/* RGB LEDS */
#define RED_PIN   14
#define GREEN_PIN 15
#define BLUE_PIN  16
void setRGB(int red, int green, int blue);

define pins as output:

void setup() {
  Serial.begin(152000);

  pinMode(RED_PIN, OUTPUT);
  pinMode(GREEN_PIN, OUTPUT);
  pinMode(BLUE_PIN, OUTPUT);
}