This isn't something you can do in any kind of general way.
In specific cases, you can use overstriking (either with an EQ field, or an
Advance field) to overlay a coloured strikethrough. This avoids most of the
positioning issues but comes a bit unstuck at line breaks.
--
Enjoy,
Tony
www.WordArticles.com
Strikethrough is part of the character, so it won't be a different
color from the rest of the character. You could use the drawing tool
to make a straight line and position it over the words to be struck
through, but keeping it aligned with them would be tricky.