Just thought I'd add a bit of clarity as to how to unlock this achievement.
In order to unlock this achievement, first press [cn_back] to access your Heroes, and then select one, then select 'Customize', then press [cn_LB].
To change your color swatch, you just have to select 'Colors' and then choose one you're not currently using. To change your hero's Symbol and Paint Pattern, you must first select a body part (for example, the right shoulder), then change the Symbol and Paint Pattern under their respective tabs. Once you've changed all three, the trophy should unlock.