Comment 4 for bug 1078664

I was confused by the old Preferences dialog referring to a "Foreground" colour for the graph thinking that this referred to the axis labels; in fact this only applied to the gridlines. I think this preference should apply to both components as using the theme foreground colour for the labels is inappropriate if transparency is used; having the pref control both allows a contrasting colour to be set by the user. I have updated the patch to enable this and clarify the wording on the preferences dialog.