Plymouth Manager – GUI tool to change initial splash screen themes in Ubuntu - Ubuntu Sharing
How To Change Ubuntu Boot Splash Screen In Plymouth? - Fosslicious
Ambiance Ubuntu Logo Splash Screen - Gnome-look.org
Bootsplash - Wikipedia
How to Customize the Ubuntu Boot Splash Screen and Logo
HOWTO] Change Ubuntu Pink/Purple Plymouth Boot screen to any color you like – The _khAttAm_ Blog
GitHub - michalpajtinka/Ubuntu-boot-splash-colour-change: How to change purple Plymouth boot screen to any colour you like (you can also change boot screen logo).