Update colors for dark theme

[klimashkin]

Hi! In the official devtool's dark theme current colors are not readable. More and more developers use dark theme now, because they got used to it in their code editors

[crysislinux]

It's a good idea.

But I am just too busy these days.

BTW, I have to work with Angular 2 these days since my boss loves it.

Anyway, PR is welcomed.

Thank you for the advice.