standard-themes

The `standard-themes' are a collection of light and dark themes for
GNU Emacs.  The `standard-light' and `standard-dark' emulate the
out-of-the-box looks of Emacs (which technically do NOT constitute
a theme) while bringing to them thematic consistency,
customizability, and extensibility.  Other themes are stylistic
variations of those or other built-in themes.

Why call them "standard"?  Obviously because: Standard Themes Are
Not Derivatives but the Affectionately Reimagined Default ... themes.