'SX DarkRes' a dark theme created by a Sony XPERIA user for Sony XPERIA devices running the latest version of Android (Oreo) and Substratum. Full instructions support change log reporting issues etc can be found at xdadevelopers - http://tinyurl.com/y8may6t3

Sony Apps

Framework (navbar size reduction)
SystemUi
Settings
Contacts
Phone
Messages

Backup & Restore
Battery Care
Calculator
Call Management
Clock
Colour Gamut and Contrast
DUALSHOCK 4
Glove mode
Home network
Package Installer
Screen Mirroring
Service Menu
SemcSettings
Smart backlight control
Smart call handling
Smart cleaner
Software update
Themes
USB Connectivity
Video image enhancement
White balance

3rd Party Apps

Gmail