How to change MSSQL Management Studio theme?

1. Install the 2010 Color Theme Editor in VS 2010.
2. Find the files somehwere in C:\Users\xxxxx\AppData\Local\Microsoft\VisualStudio\xx.x\Extensions\ .. for me, it was in \shvn3avp.com for the current version of the plugin.
3. Copy those files to a new folder: C:\Program Files (x86)\Microsoft SQL Server\xxx\Tools\Binn\ManagementStudio\Extensions\VSTheme

4. Replace extension.vsixmanifest contents with:

   <?xml version="1.0" encoding="utf-8"?>
   <Vsix xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" Version="1.0.0" xmlns="http://schemas.microsoft.com/developer/vsx-schema/2010">
   <Identifier Id="46b3817c-b0c3-42d1-8cea-d373f781b21e">
     <Name>Visual Studio Color Theme Editor</Name>
     <Author>Microsoft</Author>
     <Version>1.3</Version>
     <Description xml:space="preserve">Allows users to customize the color palette used for menus, toolbars, tabs, title bars, and other environment colors.</Description>
     <Locale>1033</Locale>
     <Icon>ThemeManagerIcon.png</Icon>
     <PreviewImage>ThemeManagerPreview.png</PreviewImage>
     <InstalledByMsi>true</InstalledByMsi>
     <SupportedProducts>
       <IsolatedShell Version="1.0">ssms</IsolatedShell>
       <VisualStudio Version="10.0">
         <Edition>Ultimate</Edition>
         <Edition>Premium</Edition>
         <Edition>Pro</Edition>
         <Edition>IntegratedShell</Edition>
       </VisualStudio>
     </SupportedProducts>
     <SupportedFrameworkRuntimeEdition MinVersion="3.0" MaxVersion="6.0" />
     <SystemComponent>true</SystemComponent>
   </Identifier>
   <References />
   <Content>
     <VsPackage>ThemeManagerPackage.pkgdef</VsPackage>
   </Content>
   

5. Import this setting: http://studiostyl.es/schemes/vs2012-dark-theme-for-vs2010

6. On the Customize Color dialog that opens on the Theme menu provided by the extension import his theme

Result:

For 2015 and SQL Management Studio 17RC1

Install the extension on VS2015 instead. Follow the above steps.

The folder on my computer was C:\Users\xxxxxx\AppData\Local\Microsoft\VisualStudio\14.0\Extensions\owbugenu.gif

The xml is:

<!-- language: lang-xml -->
<?xml version="1.0" encoding="utf-8"?>
<Vsix xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" Version="1.0.0" xmlns="http://schemas.microsoft.com/developer/vsx-schema/2010">
  <Identifier Id="B8CED2B3-FF48-4204-88E9-036CA39B83C8">
    <Name>Visual Studio 2015 Color Theme Editor</Name>
    <Author>Microsoft</Author>
    <Version>2.0</Version>
    <Description xml:space="preserve">Allows users to create and edit Visual Studio themes.  Themes can customize colors used for menus, toolbars, tabs, titlebars, the text editor, and other environment colors.</Description>
    <Locale>1033</Locale>
    <InstalledByMsi>true</InstalledByMsi>
    <SupportedProducts>
      <IsolatedShell Version="1.0">ssms</IsolatedShell>
    </SupportedProducts>
    <SupportedFrameworkRuntimeEdition MinVersion="4.0" MaxVersion="4.0" />
    <SystemComponent>true</SystemComponent>
  </Identifier>
  <References />
  <Content>
    <VsPackage>ColorThemeEditor.pkgdef</VsPackage>
    <VsPackage>Colors\Red.pkgdef</VsPackage>
    <VsPackage>Colors\Purple.pkgdef</VsPackage>
    <VsPackage>Colors\Green.pkgdef</VsPackage>
    <VsPackage>Colors\Tan.pkgdef</VsPackage>
    <VsPackage>Colors\DarkWithLightEditor.pkgdef</VsPackage>
    <VsPackage>Colors\LightWithDarkEditor.pkgdef</VsPackage>
    <VsPackage>Colors\SolarizedDark.pkgdef</VsPackage>
    <VsPackage>Colors\SolarizedLight.pkgdef</VsPackage>
    <MefComponent>ColorThemeEditor.dll</MefComponent>  
    <VsPackage>Colors\ThemeNames.pkgdef</VsPackage>
    <VsPackage>PkgDefAssemblyCodeBase.pkgdef</VsPackage>
  </Content>
</Vsix>

For latest SSMS v17.0 (or 2016) you can prematurely enable the Dark theme (apparently a work in progress?) by editing the file "C:\Program Files (x86)\Microsoft SQL Server\140\Tools\Binn\ManagementStudio\ssms.pkgundef" (as Admin) and commenting out the lines following the "Remove Dark theme" comment (approx line 241), should look something like the following after finished:

// Remove Dark theme
// [$RootKey$\Themes\{1ded0138-47ce-435e-84ef-9ec1f439b749}]
// [$RootKey$\AD7Metrics\PortSupplier\{4103F338-2255-40C0-ACF5-7380E2BEA13D}]
// [$RootKey$\External Tools\Error Loo&kup]
// [$RootKey$\LightSwitch]
// [$RootKey$\Debugger\LaunchHooks110]
// [$RootKey$\DiagnosticsHub]
// [$RootKey$\FeatureFlags]
// [$RootKey$\VB Editor]
// [$RootKey$\Languages\CodeExpansions\C/C++]
// [$RootKey$\Languages\CodeExpansions\JavaScript]
// [$RootKey$\Text Editor\C/C++]
// [$RootKey$\Text Editor\CSharp]
// [$RootKey$\Text Editor\Disassembly]
// [$RootKey$\Text Editor\ENC]
// [$RootKey$\Text Editor\JavaScript]
// [$RootKey$\Text Editor\Memory]
// [$RootKey$\Text Editor\Register]
// [$RootKey$\Text Editor\ResJSON]
// [$RootKey$\Text Editor\TypeScript]
// [$RootKey$\Text Editor\VBScript]

via https://community.spiceworks.com/how_to/136505-enable-dark-theme-in-sql-server-management-studio-2016