Short answer: not in JDS 3, as shipped with Solaris 10.
With newer versions of GNOME (those based on gtk+ 2.6 or later), such as that included in OpenSolaris, you can add the line:
gtk-alternative-button-order = 1
to your ~/.gtkrc-2.0 file to reverse the order in GNOME applications. However, the applications still have to be coded in such a way that the button order can be reversed in this way, and not all of them are.