Re: text displayed in the header line with wrong faces

[Eli Zaretskii]

> Date: Tue, 20 Dec 2016 15:57:26 +0100
> From: Ernest Adrogué <nfdisco@gmail.com>
> 
> (let ((cyan "#2aa198") (white "#ffffff"))
>   (setq header-line-format
>         (propertize
>          "abcdefghijklmnopqrstuvwxyz"
>          'face `(:foreground ,cyan :background ,white))))
>          
> It displays cyan text on white when I select any custom theme other than
> solarized, tsdh-dark or tsdh-light (the latter two are bundled with
> Emacs, I think) and white text on cyan background when I select one of
> those.

The header-line face, as defined in faces.el, inherits from mode-line,
and mode-line has the inverse-video attribute set.  When a theme
specifies both foreground and background colors for the mode-line
face, those colors specify the face completely, so the inverse-video
attribute is disabled.  But the themes you mention as deviant specify
only one of the two colors, so the inverse-video attribute stays.

You can see all this if you invoke customize-face.