Make sure you have the tool palette on display, then select the preset shape tool. The two boxes on the tool palette labelled "styles" control the colours of the preset shape. The upper one controls the stroke colour and the lower one the fill colour. Clicking on either box will bring up the colour palette so you can change the colour in that box.
Clicking on the small triangle inside each box brings up a small window with four icons in it. The right hand one of these is "null". Click on this and you will get a transparent selection. The left icon gives you colour back again. This is useful for doing hatches, you create a tool using a black stroke and a null fill.