Once you have built the Robot Workshop at any of your settlements during the “A New Threat” quest, you can then use it to build robot companions and deck them out with mods (similar to Power Armor). When using the workshop, just select “New Automatron.” From there you can begin building their various components—head, torso, arms, and legs.
While you do start off with a few mods from the get-go, you’ll have to collect more off fallen robots to unlock several more customization and modification options. Additionally, you will need junk items to build these modifications, just as if you were building Power Armor mods. Lastly, you will need specific ranks of the Science! And Robot Expert perks to build the higher end mods.
This achievement can be unlocked as early “A New Threat” when upgrading Ada. All you have to do is change her color ten times (robot paint does not require any material).
NOTE: As of May 20th, changing colors will no longer work. You must actually build 10 different mods to unlock the achievement.