In Chrome 51, Chrome's Classic Theme turned gray on Windows and Linux.
This theme brings back the blue colors from Chrome 50.
Unlike the other "Classic blue theme" extension in the Chrome Web Store, this extension does not change any other style, so you will get the modern classic theme - i.e. Chrome 50's Classic Theme.
Update (version 2): Use a subtle gradient instead of a single color to look identical to the default theme of Chrome 50 on Linux/Windows. Now the theme also works on macOS.
Extore is a team of professionals who are passionate about creating extensions for web browsers. This devotion also gives us opportunity to appreciate work of other people. We get inspired by useful, open source extensions made by developers all over the world. Our strong belief is that one should share helpful add-ons with others. That’s why we’d like to present you our ever-growing list of favourite extensions that have inspired us. Moreover, as you probably have already learned, sometimes struggling for the best brings an end to the good. Talking about add-ons it often turns out that an upgrade is worse then previous version. Also it can become really tricky to get back to the beloved version of your favourite extension. That’s why we’re going to make not only the latest, but all versions of our favourite (and we hope yours too) add-ons available for download. No more compromises, just stick to the version you really like!