highlight-changes-visibility-initial-state

highlight-changes-visibility-initial-state is a variable defined in `hilit-chg.el'.
Its value is

t

Documentation:
Controls whether changes are initially visible in Highlight Changes mode.

This controls the initial value of `highlight-changes-visible-mode'.
When a buffer is in Highlight Changes mode the function
`highlight-changes-visible-mode' is used to toggle the mode on or off.

You can customize this variable.