This achievement requires you to customize the default N7 armor, to do this go into Shepard's private quarters off the Normandy and beside the bed you will find the armor locker, access it and change any setting that is in the N7 Armour customization, This can range from color's to what armor plates are used. After doing this and saving the changes the achievement will unlock.
One thing to note is that this can be done before you meet the Illusive man the very first time, There is another armor locker behind Miranda.