Darkness of tint is measured by Visible Light Transmission percentage (VLT%). In Hawaii, this percentage refers to percentage of visible light allowed in through the combination of film and the window.
Similar to sunglass lenses, some tinting film contain metallic elements that help in reflecting incoming light and reducing the glare and heat generated by visible light.
No colors of tint are explicitly banned.
Dual side mirrors are required if back window is tinted.
Manufacturers of film do NOT need to certify the film they sell in the state.
No sticker to identify legal tinting is required.
State law does NOT allow medical exemptions that would allow you use special tint.
Window tinting laws vary from state to state and province to province. Before applying any window tinting materials, you should thoroughly review the appropriate state regulations as well as local enforcement policies to insure compliance with all applicable standards.