[v2] Add deprecated CSS system colors for testing

[reinhart1010]

I recently stumbled an old page on SitePoint which documents the use of (deprecated) CSS system color properties. The combination of those colors might have been used for fingerprinting as well.

Here's an comparison between (tested in KDE Neon, equivalent to Ubuntu 18.04 LTS / Linux):

• Firefox: Using the "Dark" theme:
  

• Google Chrome: with GTK+ Theme + Dark Mode

• GNOME Web (Epiphany), where Dark Mode (CSS Media query) has not been implemented

The combination of those colors differ between browsers and operating systems, possibly due to differences between User Agent Stylesheets (yes they exist). For example, in Firefox Preview (Android 9.0, Samsung One UI 1.0) some of those values are unsupported and return to Black #000000.