Question about Allocating

[Gan via Digitalmars-d-learn]

I've been working on my game and am getting some pretty gnarly 
memory problems. I think it's how I'm allocating.

Sometimes when I use variables I can do Color(255, 255, 255). But 
why is that different than new Color(255, 255, 255)?
Same when I'm making arrays. new int[](0) vs [].


What's the difference?