Supine-Syntax Theme
A vividly flat theme.
Supine focuses on flat and colourful, it is biased towards blue (and is great with arc gtk theme in linux)
It works extremely well with atom-material ui.
Obligatory screen shot 
Extra
The colors for primary and ascent are:
primary: #2f343f
ascent: #899ec3
Also, use contrasting panels, themed tab-bar and shadows of panels in the atom-material settings.
Made with 
by @AdiUltra