Citing the Documentation,
StyleSheetPath is a global option that specifies which directories the Wolfram System searches to find stylesheets.
The directories to be searched are specified using the FrontEnd`FileName function. Typical directories included in StyleSheetPath are FrontEnd`FileName[{$UserBaseDirectory,"SystemFiles","FrontEnd","StyleSheets"}] and FrontEnd`FileName[{$InstallationDirectory,"SystemFiles", "FrontEnd","StyleSheets"}].
In Mathematica 10.4.1 the value of this option itself is not very informative:
Options[$FrontEnd, StyleSheetPath]
{StyleSheetPath -> {ParentList,
FrontEnd`FileName[{"C:\\Program Files\\Wolfram \
Research\\Mathematica\\10.4\\SystemFiles\\Components\\MUnit\\FrontEnd", "StyleSheets"},
"PacletManager" -> True]}}
Fortunately, AbsoluteOptions works here:
AbsoluteOptions[$FrontEnd, StyleSheetPath]
{StyleSheetPath -> {
FrontEnd`FileName[{$UserBaseDirectory, "Autoload", _, "FrontEnd", "StyleSheets"}],
FrontEnd`FileName[{$UserBaseDirectory, "Applications", _, "FrontEnd", "StyleSheets"}],
FrontEnd`FileName[{$BaseDirectory, "Autoload", _, "FrontEnd", "StyleSheets"}],
FrontEnd`FileName[{$BaseDirectory, "Applications", _, "FrontEnd", "StyleSheets"}],
FrontEnd`FileName[{$InstallationDirectory, "AddOns", "Autoload", _, "FrontEnd", "StyleSheets"}],
FrontEnd`FileName[{$InstallationDirectory, "AddOns", "Applications", _, "FrontEnd", "StyleSheets"}],
FrontEnd`FileName[{$UserBaseDirectory, "SystemFiles", "FrontEnd", "StyleSheets"}],
FrontEnd`FileName[{$BaseDirectory, "SystemFiles", "FrontEnd", "StyleSheets"}],
FrontEnd`FileName[{$InstallationDirectory, "Configuration", "FrontEnd", "StyleSheets"}],
FrontEnd`FileName[{$InstallationDirectory, "SystemFiles", "Components", _, "FrontEnd", "StyleSheets"}],
FrontEnd`FileName[{$InstallationDirectory, "SystemFiles", "FrontEnd", "StyleSheets"}],
FrontEnd`FileName[{"C:\\Program Files\\Wolfram Research\\Mathematica\\10.4\\SystemFiles\\Components\\MUnit\\FrontEnd", "StyleSheets"},
"PacletManager" -> True]
}}
The built-in stylesheets are located in the directory
FileNameJoin[{$InstallationDirectory, "SystemFiles", "FrondEnd", "StyleSheets"}]
As m_goldberg correctly notes in the comment, it is strongly recommended do not edit the built-in stylesheets directly. The recommended way is to make a copy of the built-in stylesheet in the directory
FileNameJoin[{$UserBaseDirectory, "SystemFiles", "FrontEnd", "StyleSheets"}]
with another name, then remove the Saveable -> False option, and then edit it.
FileNameJoin[{$InstallationDirectory, "SystemFiles", "FrondEnd", "StyleSheets"}]– Michael E2 Apr 25 '16 at 00:38StyleSheetmodification you cannot save the modified file byMenu/File/Save. You need to useMenu/File/SaveAseven if you have already saved it once. However, I join to m_goldenberg warning: never, never changeDefault.nb. Make better something likeDefault-modified.nb, as I did for myself. You will need to assign each new notebook to this style, but you will be on the safe side. – Alexei Boulbitch Apr 25 '16 at 07:40