Microsoft has pushed out the the first new Insider Preview of Windows 10 since the OS was released to consumers; the build number for this release is 10525 and it can be downloaded now via Windows Update.
This is the first release to occur for Insiders since the release of Windows 10 on July 29th and comes from the TH2 branch which stands for Threshold 2, commonly known as, Wave 2.
In this new build there are updated color options including the ability to change the default color options. The post also says that Title Bars can now be colored as well. Microsoft also notes that there are improvements to memory manager too and you can read more about the update from the announcement post here.
Let us know if you have any issues with the install and note that this is a Fast ring release only.