Open up /etc/default/grub in a text editor with root permissions. You can do this by hitting Alt+F2 to pop up a run box, and then entering 'kdesudo kate /etc/default/grub'.
Find the GRUB_CMDLINE_LINUX_DEFAULT line as below, remove splash, then save and exit.
If you also remove quiet your boot will be very very verbose, but perhaps that's what you want?
# If you change this file, run 'update-grub' afterwards to update
# For full documentation of the options in this file, see:
# info -f grub -n 'Simple configuration'
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
At any rate, after saving your changes, open up a terminal and run the following command;
Then you should be all set.