You can customize theme colors and syntax colors live, in the settings.json file. Syntax looks like:

"workbench.colorCustomizations": { "[Monokai]": { "sideBar.background": "#347890" } }

or

"editor.tokenColorCustomizations": { "[Monokai]": { "comments": "#229977" } },

yes you can theme it live, although changing syntax colors is only possible through a (limited) json flavor of textmate.