Reduce with deconstruction or forEach - Iteration and Airbnb JavaScript Style Guide

Just use a dead simple loop:

function alwaysBlue(things) {
  const blueThings = {}
  for (const key in things) // or `for (const key of Object.keys(things))`
    blueThings[key] = 'blue'
  return blueThings
}

Those iteration methods are only good for arrays, which we aren't dealing with here.