Configuration
You can access the configuration by right clicking the ruler and selecting Options. This will then display the Options window where you can change the configuration.
Options
Theme
Allows you to change the theme of the ruler.
Location
Configuration is stored in two locations depending on if you installed from the installer or from the chocolatey package.
Installer: %appdata%\screenpixelruler\app.cfg
Chocolatey: %chocolateyinstall%\lib\screenpixelruler\tools\app.cfg