Description
This theme is exactly the one that Google put in Android M second preview and N, extended on more apps, it’s “the old” O/Pixel Dark Mode.
Now with optional Google Pixel colors and Android O style!
The theme installs through Substratum Theme Engine app, that you can download here, IT REQUIRES ROOT (except on OMS rootless and on Samsung Touchwiz Nougat system) and/or a Layers or Substratum compatible ROM: https://goo.gl/BB5eio
The theme has been tested on many ROMs, including stock Google and custom Marshmallow and Nougat ROMs (OxygenOS is supported too, it is Substratum Legacy though).
Android 6, 7.1, 7.1.1, 7.1.2 and Oreo (also with Andromeda rootless) are supported.
On 7.1-7.1.1 Substratum Legacy ROMs (including stock ones) you need to use an option called Frameworkless7.1RROcompatibility, and it has white notifications.
Sadly it isn’t possible to make them dark on that option.
Some manufacturers’ ROM’s aren’t guaranteed to be compatible (the farer they are from AOSP or Google ROMs, the more they’re likely to not be compatible. In case you end in bootloop flash the rescue zip that you find in /sdcard/Substratum/ (the substratumLegacy one if your ROM is RRO. Only most custom ROMs have OMS, the rest has RRO) and ask for refund, also by e-mail if you need.
This is the icon pack that you can see in the first screenshot, that I personally made to fit dark themes properly: https://play.google.com/store/apps/details?id=com.piereligio.darkpixelip
Themed elements:
-Pixel boot animation (on OMS only);
-Pixel and Nexus ringtones and UI sounds (on OMS only);
-14 wallpapers;
-14 accent colors (Pixel blue and Teal only, on FrameworkLess option);
-Android N-ify XPosed module;
-AOSP Contacts;
-AOSP Dialer;
-AOSP Launcher;
-AOSP Messages;
-Calculator;
-Car Throttle dark mode;
-Documents/Download UI;
-DU Updater;
-ES File Explorer;
-Facebook Messenger;
-Framework-Res;
-Gboard;
-Google Assistant;
-Google Calendar;
-Google Chrome;
-Google Chrome Beta;
-Google Contacts;
-Google Dialer;
-Google Drive;
-Google Keep;
-Google Hangouts;
-Google Inbox;
-Google Launcher/Now;
-Google Mail;
-Google Messenger;
-Google Photos;
-Google Play Console;
-Google Play Music;
-Google Play Services;
-Google Play Store;
-Google Plus;
-Google Translate;
-Instagram;
-Kernel Adiutor’s dark mode;
-LawnChair;
-N style notifications;
-Package Installer;
-Pixel Launcher;
-Root Explorer dark theme;
-Samsung Contacts;
-Samsung Keyboard;
-Samsung Phone;
-Samsung SystemUI with AOSP icons from ohayoubaka;
-Settings;
-Solid Explorer dark theme;
-Spotify;
-Substratum app;
-SuperSU;
-SystemUI;
-Telegram (join the chat group of my themes and ask for the theme there to me);
-Twitter night mode;
-WhatsApp;
-XDA Labs;
-Youtube.
Thank you all for supporting me. 
Layers Substratum AOSP UI Dark OMS RRO theme stock Marshmallow Android 6 6.0
WHAT’S NEW
580 to 582:
-Fixes in Gboard;
-Fixes in Google Contacts.
577 to 579: Fixes in WhatsApp.
574 to 576:
-Fixes in YouTube;
-Fixes in Messenger Lite;
-Fixes in Google App.
571 to 573:
-Fixes in YouTube;
-Fixes in Android System.
568 to 570:
-Fixes in Google App;
-Fixes in Google Plus;
-Fixes in WhatsApp;
-Fixes in Instagram.
565 to 567:
-Fixes in YouTube;
-Fixes in Instagram;
-Fixes in Chrome Beta;
-Fixes in Google Reply.
Screenshots
