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(dvips.info)Color subtleties

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Color subtleties
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  Color macros are defined via `\special' keywords.  As such, they are
put in the `.dvi' file only as explicit message strings to the driver.
The (unpleasant) result is that certain unprotected regions of the text
can have unwanted color side effects.  For example, if a color region
is split by TeX across a page boundary, then the footers of the current
page (e.g., the page number) and the headers of the next page can
inherit that color.  To avoid this effect globally, users should make
sure that these special regions of the text are defined with their own
local color commands.  For example, to protect the header and footer in
plain TeX, use

     \headline{\Black{My Header}}
     \footline{\Black{\hss\tenrm\folio\hss}}

  This warning also applies to figures and other insertions, so be
careful!

  Of course, in LaTeX, this is much more difficult to do because of the
complexity of the macros that control these regions.  This is
unfortunate but inevitable, because TeX and LaTeX were not written with
color in mind.

  Even when writing your own macros, much care must be taken.  The
macros that `colorize' a portion of the text work prefix the text work
by outputting one `\special' command to turn the color on before the
text, and outputting another `\special' command afterwards to restore
the original color.  It is often useful to ensure that TeX is in
horizontal mode before the first special command is issued; this can be
done by prefixing the color command with `\leavevmode'.