Color-palette/theme for Ubuntu 18.04

I have Ubuntu 18.04 installed and I like it, but I'm not a big fan of the aubergine and orange color scheme.

I tried to change it by changing the theme with the gnome-tweak-tool. The Adwaita-dark theme is basically what I'm looking for (dark grays with blue highlights). But it seems to only work on the windows and some menus. The top bar and the dock still have the old "warm gray" colors with orange highlights (e.g. orange dots next to the open applications).

Is there a way to change all the aubergine/warm-gray/orange colors to gray/blue?

Colour of the top bar and Ubuntu dock (sidebar) is dictated by the GNOME shell theme whereas I reckon you have changed only your GTK+ (application) theme to Adwaita-dark. You need to use a suitable GNOME shell theme too.

I would suggest you to use Adwaita-slim or Minwaita theme (slimmed down versions of Adwaita and both provide shell themes with dark and light variants).

See this for a guidance to change GNOME shell theme: How can I change Gnome Shell theme?