Here’s an alternative version of the Adwaita GTK theme (default in Gnome Shell) I’ve made. I changed the dark theme so it has neutral grey colors, instead of the green hues in the original.
My main reason for making this was using the dark theme with gThumb and MyPaint (hopefully Inkscape and GIMP in the future too!). The green hues of the original can affect the way you percieve hues in the image/video you’re working on, since color is interpreted in context (in this case the UI). For design work it’s always better to use neutral greys, and a brightness that matches the context where your work will be seen as good as possible.
The light version is not touched and it’s based on 3.10 (but will update soon!).
To install extract the files to /home/[user]/.local/share/themes/adwaita-neutral (use CTRL+L in nautilus to input this folder). You’ll need Gnome Tweak Tool installed to change the GTK theme (more about Gnome Tweak Tool).
If you want to know more, read about color theory on Wikipedia