Kiyran Earnshaw, 18, and a 15-year-old, who cannot be named, have changed their pleas in relation to the death of Robert Wilson at hearing a Leeds Crown Court.
Mr Wilson, 53, from Birstall, was stabbed to death outside the Thornton & Ross factory on Manchester Road, Linthwaite, Huddersfield, on January 16 this year.
His colleague John Badejo was also stabbed during the same incident.
Earnshaw, of Field Lane, Batley, appeared in via video link from custody in Manchester.
He pleaded guilty to murder and wounding with intent in relation to Mr Badejo.
The youth appeared in court via video link from Wetherby Young Offender Institution last Friday afternoon.
He pleaded guilty to murder and possession of an offensive weapon.
A date for sentencing has not been set yet but a further hearing was listed for August 14.
Mr Wilson was described as 'a loving and committed husband and father' who leaves behind a devastated wife and two stepchildren.