Opportunity is missed by most people because it is dressed in overalls and looks like work. - Thomas Edison
Yes, an underbase and for consistency and ease of production so you don't fart around with not printing this and do print that..., I'd leave it (as is) on every color. Meaning, print white ink on white...red ink on red..blue ink on blue shirts (as an example). Run that baby. You gotta print white ink anyways for the star, you use an underbase.
Well doggone I'm wrong on this one Darryl