Haw. Rev. Stat. § 286-63: Shape, size and color of plates; how affixed.

The special license plate shall be similar in shape, size and color to the regulation passenger motor vehicle number plate prescribed by law, and shall bear the official amateur radio call letters of the applicant, as assigned by the Federal Communications Commission. The special license plate shall be securely fastened to the passenger motor vehicle in lieu of the regulation number plate; provided that the regulation tag or emblem issued each year shall be affixed to the passenger motor vehicle or the special license plate in the manner provided in section 249-7.