How do I make random choice when playing script on console?

So basically, my script places random bets on a website and I want it to choose it randomly EVERY bet and I wanted to make it random choice between 'red' and 'black' so i did

var betColor = 'random.nextBoolean() ? red : black;';

But it choose the color randomly, and used it for all the bets, I want it to choose randomly every bet. Any help?