Re: The color of a header line and window selection.

[Richard Stallman]

    Under X, in a frame with multiple windows, the mode line of the
    selected window will be darker than the mode lines of the other
    windows.  A header line, however, always has the light color.  Is
    there a reason why the header line should behave differently?

The header line is not used like the mode line.  Most windows don't
have header lines, and those that do, use them to go with the text
in the window rather than to say what the window is showing.
So I think they should not change color.