Different folders in 15 colors.
Copy the color you like and paste it into the "places" directory of the active theme.
The active theme is located in the ./local/share/icons or /usr/share/icons directory.
You can also learn the active icon theme with the command below.
grep 'gtk-icon-theme-name' $HOME/.config/gtk-3.0/settings.ini | sed 's+.*=++g'
You can find out the active theme with the theme manager.