Preferences and templates
There are several ways to control the style of a freshly created graph.
First, you can capture specific elements of a sample graph as global preferences. From then on, unless you turn off preferences, all graphs that are created by the New Graph dialog will take on the styles you specified.
Second, you can build an example graph exactly as you want future graphs to appear and then create a named template that you can specify in the New Graph dilaog.
Finally, since Igor is highly programmable, you can create macros that can impose a style on an existing graph. Style macros are done this way except they are written automatically by Igor rather than by you.