implicitIteration.js

colors.forEach((color) => {
  console.log(color);
});

// You use closures and arrow functions

1. You want to use of with iterators, in is for string keys of objects (including inherited).
2. for in and for of syntax in js looks like for (const ident of expression)
   (where const could be let or var and of could be in)
3. there's a missing ) in the last statement
4. most commonly available print fn in js is console.log
5. Array method is called forEach (capitalization)

so, all in all:

const colors = ['red', 'green']
const {log} = console

for (const color of colors)
  log(color)

// closure/arrow function
colors.forEach(color => log(color))