The swap fill and stroke tool does exactly what you would expect. It's just a matter of finding it on the page. Draw a square, use (V) to select it then swap fill/stroke.

This tool is part of the Color tools

Next click the fill box. A new pop up will appear on the right side of the screen. This allows you to adjust color using the CMYK (Cyan, Magenta, Yellow, Black). CMYK is what most printers will print with.

To choose a color you can input or adjust the sliders for each of the four colors, or you can pick a color from the CMYK spectrum at the bottom of this popup.

If you prefer not to use CMYK or you know the application you are using it for isn't CMYK friendly you can change it. Click the menu bar and you will have several other options to play with.