Source: http://www.engadget.com/2013/10/01/google-docs-gets-a-facelift/
You can't say that the Google Drive crew isn't looking out for you. Following the transition of QuickOffice for Android and iOS into a freebie, the team is now blessing Google Docs with a slightly more attractive interface. First and foremost, you'll now find a familiar, colorful product icon in the upper left part of the web app, which links back to Drive. This refinement applies to Docs, Sheets, Slides, Drawings, Forms and Apps Script, and it could very well help users of another office suite feel more at home. Additionally, the headers within each of the editors are now more compressed, which Google hopes will allow users to focus more easily on their content. Naturally, these aren't the most dramatic visual changes, but then again, do you really want a card-based UI for your document editor?
Source: Google Drive Blog