Tim:
Older versions of Linux did let you tweak GUI palettes, etc., with an editor, quite easily. You had more than just the choice of several prepared themes.
Eur Ing Chris Green:
What's this about "Older versions of Linux did let you ....", it's just as possible now if you get away from the default Gnome/KDE desktops. I'm running fvwm2 on this FC6 system and have all the 'old fashioned', very simple, ways to set colours etc.
Back when I tried Red Hat 6.0 Linux, using Gnome, I could do so. Now, I can't.