Can I be sued after being found not guilty for using racial slurs?

Yes, although I'm not sure what the claim would be.  Possibly intentional infliction of emotional distress.  Being found not guilty of a crime means only that the prosecution was unable to prove its case beyond a reasonable doubt.  However, a civil plaintiff does not need to prove his/her/its claim beyong a reasonable doubt but only, in most cases, by a preponderance of the evidence.  Since a lesser standard of proof applies, being found "not guilty" does not necessarily mean that you are not civilly liable.