How do I disable Dock and Panel transparency?

Solution 1:

To force Ubuntu Dock to assume a fixed opacity, open Terminal and run

gsettings set org.gnome.shell.extensions.dash-to-dock transparency-mode 'FIXED'

Also you can change max-alpha and min-alpha (0 is completely transparent, 1 is completely opaque) of Ubuntu Dock following this:
How to make Ubuntu Dock fully opaque (black, like the top bar) when apps are touching it/fullscreen?

Getting rid of top-bar transparency is a bit tricky. You may use "Dynamic Panel Transparency" extension from here.

Once installed reload the page, a settings icon should appear. Click on it, a dialogue should pop up. Go to Background tab, toggle on "Enable custom opacity" and set "Unmaximized opacity" to a very high value, say 100%.

Then log out and log in again.

Alternatively you may try a different shell theme without a transparent top bar.