Anno 1800
How do the three free upgrades on a population card work?
The rulebook limits free upgrades to the depicted cubes; the single-step details come from agreeing forum posts.
They are three separate single steps that cost nothing, and they may only improve the cube colours shown on the card. One cube can take more than one step, and steps can go to different cubes, so a farmer needs two steps to reach an artisan. A step cannot jump past a colour, so a green cube cannot reach purple from one card. You may mix green-to-blue and blue-to-red steps.