A new build of Windows 10 has started to show up in various places around the web and we have already seen how the Recycle Bin icon has been updated. Digging a bit deeper into the OS, we can see that there are also new themes and customization options.
The biggest change with the themes comes with the Action Center, where the color of the panel will now match the theme that you choose. As you can see from the image below, if you select the black theme, the panel will now match.
In addition to the new themes, you now have the option to customize where your theme color is applied. If you take a look at the image below, you can see the three new options including turning transparency on and off.
It also looks like from the options you can set the window border color so it will not always be the boring drab grey.
All of these features will be coming to Insiders in a future release and should be a welcomed addition to the OS. There's no indication that this build will leak in the near future but seeing how quickly Windows 10 builds have been rolling out, we may not have to wait too long for an official build.
Source: ITHome (Chinese)