Since humans can only see to 380 nanometers (violet), but tetrachromats can see into the ultraviolet to about 300 nanometers, this fourth primary color for tetrachromats is located in the shorter-wavelength range.
Since humans can only see to 400 nanometers (violet), but tetrachromats can see into the ultraviolet to about 300 nanometers, this fourth primary color might be located in the shorter-wavelength range.