FYI the images ./gtk-2.0/Expanders/minus.svg and ./gtk-2.0/Expanders/plus.svg are hardly visible in Thunderbird Folder Tree. With my elementary level Inkscape skills, I opened these 2 files and changed the opacity value to 70%, the Fill K value to 65, and the Stroke K value to 70. I hope this doesn't create problems elsewhere ;-) Maybe you might have a better solution? Or maybe it's better to keep those pale arrows in Thunderbird?
FYI the images
./gtk-2.0/Expanders/minus.svgand./gtk-2.0/Expanders/plus.svgare hardly visible in Thunderbird Folder Tree. With my elementary level Inkscape skills, I opened these 2 files and changed the opacity value to 70%, the Fill K value to 65, and the Stroke K value to 70. I hope this doesn't create problems elsewhere ;-) Maybe you might have a better solution? Or maybe it's better to keep those pale arrows in Thunderbird?