
Kubuntu allows themes to be changed simply. Go to the Kickoff Application Launcher (K Menu)
Click System
Open System Settings.
In the left-hand pane, click Appearance, then to go the Workspace Tab at the top.
From here, it's possible to choose from the list of installed themes.
To install a new theme, click on the button at the bottom right.
From here, pick the source and run a search for the desired theme.
Once the theme is downloaded and installed, it can be picked from the list of installed themes.