How do I change the palette in C2's image editor?

I've searched all over for this and couldn't find the answer though I'm sure it's been answered before. I want to limit the palette in my game so I only have the same colors as a NES would have, like this.

Now:

I'd like it to be like this:

Is this possible?

That would be rather neat to have, even better if the palettes were editable/saveble/loadable.