Randomly Alternate LED pins

Using Arduino LEDs and Multiplexing
18

Thank you to everyone for your helpful comments. This isn't a programming language I have used much before so the little things become frustratingly invisible.

Below is the code that achieves my desired output for any future reference:

unsigned long previousMillisLED10 = 0; //millis() returns an unsigned long
unsigned long previousMillisLED11 = 0; //millis() returns an unsigned long

unsigned long intervalLED10 = 100; //time needed to wait (ms) - 10 Hz
unsigned long intervalLED11 = 1; //1 kHz

boolean LED10State = false; //state variable for LED
boolean LED11State = false;

int ledPin1;
int ledPin2;

void setup() {
  // put your setup code here, to run once
Serial.begin(9600);
pinMode(ledPin1, OUTPUT);
pinMode(ledPin2, OUTPUT);  

int myPins[]={10, 11};

randomSeed(analogRead(A0));

ledPin1 = myPins[random(0,2)];

   if(ledPin1 == 10){
  ledPin2 = 11;} 
  else if (ledPin1 == 11){
    ledPin2 = 10;}

Serial.print("Pin 1: " );
Serial.println(ledPin1);
Serial.print("Pin 2: " );
Serial.println(ledPin2); 
}

void loop() {
  // put your main code here, to run repeatedly:
  

    

unsigned long currentMillis = millis(); //grab current time
//toggle LED10
if ((unsigned long)(currentMillis-previousMillisLED10)>= intervalLED10){
  LED10State =!LED10State; //toggles the state
  digitalWrite(ledPin1, LED10State); //sets the LED based on ledState
  //save the 'current' time to pin 10's previousMillis
  previousMillisLED10 = currentMillis;
}
//toggle LED11
if ((unsigned long)(currentMillis-previousMillisLED11)>= intervalLED11){
  LED11State =!LED11State; //toggles the state
  digitalWrite(ledPin2, LED11State); //sets the LED based on ledState
  //save the 'current' time to pin 11's previousMillis
  previousMillisLED11 = currentMillis;
}
}