How do I customize PDF-XChange Viewer Tools UI appearance?

I don't like the default "style of appearance" on one of the object tools and want to change it.

Most objects in PDF-XChange Viewer can have their appearance customized.  Typically this is done by creating an instance of that object on a page, selecting it and using the right mouse button clicking 'Properties' to open the object's Properties dialogue box.  From here you can change the attributes of the object including it's appearance.

Alternately:

To select an object for modifying switch to the select tool  and single left click the object.  

After doing so you will see the context sensitive "Properties" tool bar change to display the editable components of that object

: 

Use this to modify your objects appearance.  Once you are satisfied with it you can save it as the default style for that object.

Having modified a single instance of the object one can now select "Set Current Appearance as Default" from the context menu (right click an object for context sensitive options).  Certain attributes will even be reflected in the appearance of the Tool Bar Icon.  Setting the "val Tool" default colour property to green will result in a green "Oval Tool" icon on the toolbar for example.  Note that this procedure will only modify the object properties and NOT the text within text enabled objects. 

To set the default style of text within such an object like the "Typewriter Tool" or the "Text Box Tool" see this article: 

KB#140: How do I change the default text used in the typewriter or text box tools?