colorListOneLiner.js

/**
 * one-line solution with sets!
 */

const oneliner = [...new Set(colors.split(' '))].join(' ');
console.log(oneliner);

/**
 * WHOAH! let's break that down!
 */

// break up the string on spaces
const colorArray = colors.split(' ');

// use the Set constructor to convert the array into a non-repeating set
// @see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set#Description
const colorSet = new Set(colorArray);

// we want to destructure the set into an array then join into a string
const solution3 = [...colorSet].join(' ');

console.log(solution3);