Expungement is the removal of an offense, usually a conviction (and anything relating to the offense) from your records, although the fact that "something" was expunged may still appear (although not what that something is). Sealing is officially preventing all access to the records without a court order. These terms are often used interchangeably, and the petition you will need to fill out in Colorado is the same for either.
You can have your record either expunged or sealed under Colorado Rev Stat 19-3-313. With either an expungement or sealing, the records are still accessible by court order, and expunged records are accessible by law enforcement or through statutory authority. Both essentially mean that records of your arrest, detention, trial, disposition, etc. are not available to the public, they are erased from all public records, and it is as if they did not occur.
To have records sealed or expunged, you do not contact the judge. You must file a "petition to seal" with the court (CRS 24-72-308). Petition forms should be available at the court.
The clerk will fill in the case number and you must FULLY fill out the rest. All blanks must be filled. If you are unsure what to fill in in a certain blank, ask the court clerk.
You must specify which criminal justice agency has your records and the specific file numbers for any arrest or court case that you want sealed (available from the arresting agency or the clerk's office). List the result of the official action you are petitioning to seal.
Sign the petition in front of a notary public or the court clerk. Submit the forms with your filing fee.
Once the petition and forms are submitted, the court will set up a hearing date. You appear at the hearing and the judge will either grant or deny your petition. If all charges against you were dismissed, your petition to have your records sealed should be granted.
