Chrome announced this experimental feature in December 2013, and there is a lot of themes already on the Chrome Web Store for download.
To enable this feature, just
- open your DevTools (ctrl/cmd)-alt-i,
- go to settings,
- click the Experiments tab,
- check the “Allow Custom UI themes”,
- then install a theme from web store,
I like this one https://chrome.google.com/webstore/detail/devtools-theme-zero-dark/bomhdjeadceaggdgfoefmpeafkjhegbo.
When you installed a theme, you have to restart chrome, and when open the devtools again, you can see the inspector applied the theme that you installed.
