Matter of fact, a tool named qt3-qtconfig can be used to adjust the QT 3 program appearance. The modification will be applied onto all QT 3 programs in the system. Use apt-get to install the tool.
:/$ sudo apt-get install qt3-qtconfig
I suggest the theme "polymer" for QT 3. Use apt-get to install the theme.
:/$ sudo apt-get install polymer
After they are installed, run "qtconfig-qt3" to apply the "polymer" theme. Actually, with the tool it is also possible to specify Font Family used for QT 3 programs. I prefer 'Bitstream Vera Sans' size 9. You can choose whatever you like.
I have turned to SALOME 5.1.1 already. It is therefore a pity that I cannot take screenshots to show the effect. Please try to see if you are interested.