Windows Classic For Windows 10

Mass Transit Honchkrow a preview depicting the various color schemes in the modern UI. Clarification that these methods still work. Microsoft is considering making drastic changes to file explorer. I will inform you if those changes break this advice.
Other websites may have this info, but this will work past build 14393, and it works on Build 19041, which I'm running at editing time. You must have a shell reference in order to access these older menus. My theme publishing is made easier by these native tools. I try to avoid using third party apps as they require security sacrifices.
While themes are labeled "Classic", they apply as High Contrast, a non-3D implementation of the MDL UI present since Windows 8.
They should be extracted to %SystemRoot%\Resources\Ease Of Access Themes\. Placing them in this directory requires elevation and makes them less prone to accidental deletion. You can place them in your user theme directory if you don't want to touch system files.
To access the old Personalization Panel, you'll need to create a new shortcut and place this in the target line:

To access the old Color Picker, you'll need to create a new shortcut with this target line:

If any substantial changes occur to the MDL UI, these menus might vanish.