how do i go about changing these?
Do you mean the indicators
or an actual button somewhere ?
The following example is for the classic theme indicators -
Edit the appropriate equivalents for your theme & language(s).
Backup the originals first, then edit the following.
Example -
Indicators - Displayed in front of each board row.
forum/Themes/classic/images/on.gif (contains new messages)
forum/Themes/classic/images/off.gif
Key - displayed below forum boards main page
forum/Themes/classic/images/english/new_some.gif
forum/Themes/classic/images/english/new_none.gif
HTH
Paul