Imagination is everything! The RGBA patch didn't seem to change anything - no matter what (with Xrdb, fonts.conf) font rendering always stays on rgb.

The radiance problem was text shadows. Please see attached screenshot of screenshots: it's color enhanced. The upper part is a menu bar item with text-shadow the lower one without.

Here is an overview of the changes:

/usr/share/themes/Radiance$ grep -iR text-shadow *gtk-3.0/gtk-widgets.css.orig:    text-shadow: 0 1px shade (@bg_color, 1.04);
gtk-3.0/gtk-widgets.css.orig:    text-shadow: 0 1px alpha (shade (@button_bg_color, 1.25), 0.4);
gtk-3.0/gtk-widgets.css.orig:    text-shadow: 0 1px alpha (shade (@button_bg_color, 1.25), 0.2);
gtk-3.0/gtk-widgets.css.orig:    text-shadow: 0 1px alpha (shade (@button_bg_color, 1.25), 0.4);
gtk-3.0/gtk-widgets.css.orig:    text-shadow: 0 1px alpha (shade (@button_bg_color, 1.25), 0.2);
gtk-3.0/gtk-widgets.css.orig:    text-shadow: 0 1px alpha (shade (@bg_color, 1.25), 0.4);
gtk-3.0/gtk-widgets.css.orig:    text-shadow: 0 -1px shade (@dark_bg_color, 0.6);
gtk-3.0/gtk-widgets.css.orig:    text-shadow: 0 -1px shade (@dark_bg_color, 0.8);
gtk-3.0/gtk-widgets.css.orig:    text-shadow: 0 -1px shade (@dark_bg_color, 0.7);
gtk-3.0/gtk-widgets.css.orig:    text-shadow: none;
gtk-3.0/gtk-widgets.css.orig:    text-shadow: 0 -1px shade (@selected_bg_color, 0.7);
gtk-3.0/gtk-widgets.css.orig:    text-shadow: 0 -1px shade (@dark_bg_color, 0.6);
gtk-3.0/gtk-widgets.css.orig:    text-shadow: 0 1px shade (@bg_color, 1.14);
gtk-3.0/gtk-widgets.css.orig:    text-shadow: 0 -1px shade (@dark_bg_color, 0.7);
gtk-3.0/gtk-widgets.css.orig:    text-shadow: 0 1px shade (@selected_bg_color, 0.7);
gtk-3.0/gtk-widgets.css.orig:    text-shadow: 0 1px alpha (shade (@bg_color, 1.25), 0.5);
gtk-3.0/gtk-widgets.css.orig:    text-shadow: 0 1px shade (@selected_bg_color, 0.7);
gtk-3.0/gtk-widgets.css.orig:    text-shadow: 0 1px alpha (shade (@bg_color, 1.25), 0.5);
gtk-3.0/gtk-widgets.css.orig:    text-shadow: 0 1px alpha (shade (@button_bg_color, 1.25), 0.4);
gtk-3.0/gtk-widgets.css.orig:    text-shadow: 0 1px alpha (shade (@button_bg_color, 1.25), 0.2);
gtk-3.0/gtk-widgets.css.orig:    text-shadow: none;
gtk-3.0/gtk-widgets.css.orig:    text-shadow: 0 -1px shade (@dark_bg_color, 0.7);
gtk-3.0/gtk-widgets.css.orig:    text-shadow: 0 -1px shade (@dark_bg_color, 0.7);
gtk-3.0/gtk-widgets.css.orig:    text-shadow: 0 -1px shade (@dark_bg_color, 0.7);
gtk-3.0/gtk-widgets.css.orig:    text-shadow: 0 -1px shade (@dark_bg_color, 0.9);
gtk-3.0/gtk-widgets.css.orig:    text-shadow: 0 -1px shade (@dark_bg_color, 0.6);
gtk-3.0/gtk-widgets.css.orig:    text-shadow: none;
gtk-3.0/gtk-widgets.css.orig:    text-shadow: none;
gtk-3.0/gtk-widgets.css.orig:    text-shadow: none;
gtk-3.0/gtk-widgets.css.orig:    text-shadow: none;
gtk-3.0/gtk-widgets.css.orig:    text-shadow: 0 1px alpha (shade (@bg_color, 1.25), 0.5);
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets.css:    text-shadow: none;
gtk-3.0/gtk-widgets-radiance.css.orig:    text-shadow: 0 1px shade (@dark_bg_color, 1.1);
gtk-3.0/gtk-widgets-radiance.css.orig:    text-shadow: 0 1px shade (@dark_bg_color, 1.1);
gtk-3.0/gtk-widgets-radiance.css.orig:    text-shadow: 0 -1px shade (@selected_bg_color, 0.7);
gtk-3.0/gtk-widgets-radiance.css.orig:    text-shadow: 0 1px shade (@bg_color, 1.14);
gtk-3.0/gtk-widgets-radiance.css.orig:    text-shadow: 0 1px shade (@dark_bg_color, 1.1);
gtk-3.0/gtk-widgets-radiance.css.orig:    text-shadow: 0 1px shade (@dark_bg_color, 1.1);
gtk-3.0/gtk-widgets-radiance.css.orig:    text-shadow: 0 1px alpha (shade (@dark_bg_color, 1.25), 0.32);
gtk-3.0/gtk-widgets-radiance.css:    text-shadow: none;
gtk-3.0/gtk-widgets-radiance.css:    text-shadow: none;
gtk-3.0/gtk-widgets-radiance.css:    text-shadow: none;
gtk-3.0/gtk-widgets-radiance.css:    text-shadow: none;
gtk-3.0/gtk-widgets-radiance.css:    text-shadow: none;
gtk-3.0/gtk-widgets-radiance.css:    text-shadow: none;
gtk-3.0/gtk-widgets-radiance.css:    text-shadow: none;
gtk-3.0/apps/unity.css.orig:    text-shadow: 1px 0 shade (@dark_bg_color, 1.06), -1px 0 shade (@dark_bg_color, 1.06),
gtk-3.0/apps/unity.css.orig:    text-shadow: 1px 0 1px shade (@dark_bg_color, 1.08), -1px 0 1px shade (@dark_bg_color, 1.08),
gtk-3.0/apps/unity.css.orig:    text-shadow: 1px 0 shade (@dark_bg_color, 1.06), -1px 0 shade (@dark_bg_color, 1.06),
gtk-3.0/apps/nautilus.css.orig:    text-shadow: 1px 1px alpha (#000000, 0.8);
gtk-3.0/apps/nautilus.css.orig:    text-shadow: none;
gtk-3.0/apps/nautilus.css.orig:    text-shadow: 0 1px shade (@cluebar_color, 1.06);
gtk-3.0/apps/nautilus.css.orig:    text-shadow: 0 1px shade (@cluebar_color, 1.02);
gtk-3.0/apps/nautilus.css.orig:    text-shadow: 0 1px shade (shade (@bg_color, 0.95), 1.04); 
gtk-3.0/apps/nautilus.css.orig:    text-shadow: 0 1px shade (shade (@bg_color, 0.95), 1.02); 
gtk-3.0/apps/nautilus.css.orig:    text-shadow: 0 1px shade (@selected_bg_color, 0.8); 
gtk-3.0/apps/nautilus.css.orig:    text-shadow: 0 1px shade (shade (@bg_color, 0.95), 0.96); 
gtk-3.0/apps/unity-greeter.css:    text-shadow: none;
gtk-3.0/apps/unity.css:    text-shadow: none, none;
gtk-3.0/apps/unity.css:    text-shadow: none, none;
gtk-3.0/apps/unity.css:    text-shadow: none, none;
gtk-3.0/apps/gnome-panel.css.orig:    text-shadow: none;
gtk-3.0/apps/gnome-panel.css.orig:    text-shadow: 0 1px shade (@dark_bg_color, 1.08);
gtk-3.0/apps/gnome-panel.css:    text-shadow: none;
gtk-3.0/apps/gnome-panel.css:    text-shadow: none;
gtk-3.0/apps/nautilus.css:    text-shadow: none;
gtk-3.0/apps/nautilus.css:    text-shadow: none;
gtk-3.0/apps/nautilus.css:    text-shadow: none;
gtk-3.0/apps/nautilus.css:    text-shadow: none;
gtk-3.0/apps/nautilus.css:    text-shadow: none;
gtk-3.0/apps/nautilus.css:    text-shadow: none;
gtk-3.0/apps/nautilus.css:    text-shadow: none;
gtk-3.0/apps/nautilus.css:    text-shadow: none;
mt@nPong:/usr/share/themes/Radiance$ 



PLEASE consider using bold fonts with backgrounds instead of text shadows.