Slackware normally sets an alias for 'ls' in the profile file for 'login shells', but konsole doesn't start a 'login shell' by default, so you don't get it. Some folks suggest changing the konsole preferences so that it starts a 'login shell' to workaround this issue. Personally, I don't like that idea.
Add the following to your $HOME/.bashrc file (if you don't have one just create one):
Code:
alias ls='ls --color=auto'
The next time you start konsole you'll get your colour ls output.