Menu > More Applications > Configuration > EZswitch. --- You can switch between the themes that you have installed using this app. It will generate a list of the themes you have installed from which you can choose a theme to use.
Open your terminal (konsole for KDE users) and enter these commands --
give root password at the prompt --
You can skip this step, but it is beneficial in that it helps to keep your initrd.img from becoming too large.
Instead of >>name-of-theme<<, use the name of the theme you are switching to. -- Note that the names are case sensitive. The name you enter must be an exact match to the name of the theme folder in /usr/share/plymouth/themes. Examples: PCLinuxOS, LXDE-Flight, legacy and RadicallySimple.