Created attachment 132653 [details]
See the screenshot.
White background and black foreground is hard-coded in netbeans.css style sheet that's being used in NetBeans helpsets. I can remove the hardcoded colors to revert to the default ones but there's a risk that the help pages won't be readable in some special color themes (e.g. GTK on Linux). If user's default background is e.g. light blue then all hyperlinks will be almost invisible.
I suggest leaving Help window as it is now. I don't think it's used that often and it usually doesn't stay open for too long either.
Dark themes were moved to the NetBeans Update Center for NB 7.4