Requirements:
1. Android Version & ROM:
a) Stock Android 6.0.X (Marshmallow) Rom -> Substratum Legacy (only Overlays; Reboot needed)
b) Stock Android 7.0 (Nougat) Rom -> Substratum Legacy (only Overlays; Reboot needed)
c) Layers compatible Android 6.0.X (Marshmallow) Rom -> Substratum Legacy (only Overlays; Reboot needed)
d) Substratum (OMS) compatible Android 6.0.X (Marshmallow) Rom -> Substratum (Overlays, Fonts, on the fly changing)

3. Display Density:
- xhdpi, xxhdpi or xxxhdpi device, most things should work on lower densities too

3. Theme Engine App:
- Substratum (min Version: 135)

Outline contains about 65 Overlays:

35 Overlays for Third Party Apps

20 Overlays for Google Apps

Overlays for 10 System Apps

To see which apps are themed have a look here: https://goo.gl/2ZvIGT

Choose between many colors (Outline, Material & Pastel versions of most colors) and mix and match them by choosing your accent and primary color.
Color preview: https://goo.gl/KIozzY (outdated)

Community & Support: goo.gl/aBnG0m

Setup used for the screenshots:
Action Launcher 3 (https://goo.gl/ZGZR4U)
Magme icons (https://goo.gl/Mi25HX)