I'd like to change the background color of the purple plymouth boot splash to another color, how can I do this?
It's pretty easy.
Open the file
save the file and run the following command.
The background of the boot splash should now be black instead of purple.
ahhh heck, if you prefer to use a GUI then go with the plymouth manager app. It should be pretty strait forward and it lets you make a custom theme or pick one of the ones offered. http://www.omgubuntu.co.uk/2010/11/plymouth-manager-lets-you-change-boot-theme-resolution-in-ubuntu/