Google began a Material Theme refresh of its desktop search UI last fall comprising tweaks all users see now, including a search "box" with rounded corners, more white, and a persistent search bar. The next step may be nigh, as the search engine is testing the addition of Material Theme icons that sit beside each search menu filter (e.g., News, Maps, Images, etc.) and are colorized when their corresponding filter is active.
When a search filter is being used on Google.com (like the default "All" filter, as seen in the screenshot below), the relevant icon in the new test will come to life in Google brand palette colors; the icons for inactive filters are gray.
Google's latest test featuring icons next to each search filter (top) vs. the current layout (bottom)
The test was first pointed out by Twitter user @YoungbloodJoe, who saw the change in the midst of a search session.
It literally just changed for me a few minutes ago. I typed a search on old menu design and it displayed SERPs in new design.
— Joe Youngblood (@YoungbloodJoe) March 28, 2019
The pop of color is a nice, inoffensive addition to Google's search engine results pages, and it'll probably make it easier for users to more quickly find filters of interest for their present query. It also falls in line with some of Google's recent redesigns, which have come with similar Material-y icons in tow. And some of these search filter icons almost exactly mirror recently updated app icons (like News and Shopping). That said, this test hearkens back to 2010, when Google first rolled out color icons for its left-hand search options column for desktop-based queries. (Those lasted less than a year before being removed.)
As I type this post, I don't see these Material Theme icons when I open the search engine on either of my laptops, regardless of what browser I use. This appears to be a test with a rather narrow set of users for now, but if you see it, let us know in the comments.