Hello, I am a beginner in Sony Vegas and I would like to ask some questions about masking.

So when I used the anchor creation tool and outlined it on a person and then connected the first dot with the last dot, it worked. But the area excluded from where I made a mask isn't transparent, it's black. Even when I put a solid color underneath it, it's still black.

Can anyone tell me how to fix this? Thank you.

EDIT:

Yes, exactly, it's plain black. It isn't transparent like how it is supposed to be. So the solid color that I prepared underneath it doesn't show. BTW I'm trying to do the "contours effect"

Thank you so much.