How should I wash this top?

[fadingfast]

Any laundry gurus out there? I have a new work top which is one of those looks-like-two-but-only-one tops. The 'shirt' bit is white, the cotton tank top bit is black.

Soooo do I wash it with whites or colours?

This is really stressing me out.

with darks and with one of those colour catcher things. if you put it in with whites it could turn them all grey