Preview: Change the Fill option for the Annotate tool

I enabled the annotate option on the Tools for Mac Preview Application and now I cannot draw a rectangle without the Fill option. How can I get rid of the Fill option so that I can draw a rectangle without filling the contents in it.

Here is the example of a filled rectangle in it.

The fill colour is in the same toolbar, see pic…

[Edit - updating for Yosemite, Mavericks is below…)

Yosemite -

1. Show Toolbar
2. Fill drop-menu
3. Transparent is the one with the red line through, top left of the colour-picker.

Mavericks -

1. Rectangle tool.
2. Fill colour
3. Transparent is the one with the red line through, top left of the colour-picker.