I don't know if it's the longest, but its dominant wavelength is around 625-740 nanometers.
It does - you are smart!  The wavelength is 625-740 nanometres!
Red is such a passionate, vibrant color Oh, that's nice. It sits next to orange at the end of the spectrum of visible light. It has the longest wavelength from what I can remember!
It has a dominant wavelength of approximately 625–740 nanometres.