Google's help centers have switched to Material Design. Help centers use different colors, much like the mobile apps. Gmail's help center uses a red background for navigation elements and it's annoying because it distracts you from the article.
Chrome's help center uses blue and it's interesting to notice that the sidebar stands out more than the article. There are many other services that have blue help centers: Search, Calendar, AdWords, AdSense, AdWords, Maps.
Here's the homepage for Google Drive's help center. The transition between Google's help centers is jarring because they look so different now. Colors should be used sparingly and shouldn't distract from the main content.