There is a way to increase the space before the text, though I have not found a way to control the colour of this space yet.
The margins in Notepad++ can be changed using macros. Open up your shortcuts.xml. This can be found in %APPDATA%\Notepad++\shorcuts.xml. The copy in Program Files (x86)\Notepad++\... is a template.
Add the following macro inside the <Macros> node of the xml then restart Notepad++.
<Macro name="Increase Margin" Ctrl="yes" Alt="yes" Shift="no" Key="39">
<Action type="0" message="2242" wParam="3" lParam="20" sParam=""/>
</Macro>
This will create a new macro with shortcut Ctrl+Alt+Right that sets the width of the Fold margin to 20px (lParam). The shortcut can be changed easily from within Notepad++ by going into Macro->Modify Shortcut and changing the buttons required. This will need to be run
each time that Notepad++ is started, however.
Further info on how to tweak the macro can be found in the above link