Haw. Rev. Stat. § 387-4

No employer shall discriminate in any way in the payment of wages as between persons of different races or religions or as between the sexes; provided that nothing herein shall prohibit a variation of rates of pay for employees engaged in the same classification of work based upon a difference in seniority, length of service, substantial difference in duties or services performed, difference in the shift or time of day worked, or hours of work; and provided that an employer who is paying a wage rate differential in violation of this section shall not, in order to comply with this section, reduce the wage rate of any employee.