Silverlight 4 now allows you to define “implicit styles” for your applications.  This allows you to style controls by type (for example: have a default look for all buttons) and avoid you having to explicitly reference styles from each control. 

In addition to honoring implicit styles on the designer-surface, VS 2010 also now allows you to right click on any control (or on one of it properties) and choose the “Go to Value Definition…” context menu to jump to the XAML where the style is defined, and from there you can easily navigate onward to any referenced resources.  This makes it much easier to figure out questions like “why is my button red?”: