Why I change value in my new array but my default array change as well

Question

I am trying to write a function to make the test case pass but when I tryna change value in my new arreay it make my default array change as well.

Here is my function:

function paintShop(cars, colour) {
  let paintedCar = [];
  for (var i = 0; i < cars.length; i++) {
    if (cars[i]["colour"] === "Red") {
      paintedCar.push(cars[i]);
      paintedCar[0]["colour"] === "Pink";
    }
  }

  console.log("colour", colour);
  console.log("paintedCar`", paintedCar);
  console.log("cars", cars);
}

paintShop(
  [
    { make: "Ford", model: "Fiesta", colour: "Red" },
    { make: "Land Rover", model: "Defender", colour: "Muddy" },
    { make: "Toyota", model: "Prius", colour: "Silver" },
    { make: "Honda", model: "Civic", colour: "Yellow" },
  ],
  "Pink"
);

module.exports = paintShop;

and here is my test cases:

var paintShop = require("./paint-cars");

test("Paint shop", function () {
  var cars = [
    { make: "Ford", model: "Fiesta", colour: "Red" },
    { make: "Land Rover", model: "Defender", colour: "Muddy" },
    { make: "Toyota", model: "Prius", colour: "Silver" },
    { make: "Honda", model: "Civic", colour: "Yellow" },
  ];

  var unpaintedCars = [
    { make: "Ford", model: "Fiesta", colour: "Red" },
    { make: "Land Rover", model: "Defender", colour: "Muddy" },
    { make: "Toyota", model: "Prius", colour: "Silver" },
    { make: "Honda", model: "Civic", colour: "Yellow" },
  ];

  var repaintedCars = [
    { make: "Ford", model: "Fiesta", colour: "Pink" },
    { make: "Land Rover", model: "Defender", colour: "Muddy" },
    { make: "Toyota", model: "Prius", colour: "Silver" },
    { make: "Honda", model: "Civic", colour: "Yellow" },
  ];

  var output = paintShop(cars, "Pink");

  // expect(output).toEqual(repaintedCars);
  expect(cars).toEqual(unpaintedCars);
});

Can anyone help me solve this problem????