What color of light has the highest frequency?

Violet
Violet has the highest frequency, and red has the lowest frequency.
Think about VIBGYOR. It has colors ordered from highest to lowest frequency.
Violet
Indigo
Blue
Green
Yellow
Orange
Red
For light, its speed ##c## = ##f*lambda##
where ##f## is frequency and ##lambda## is wavelength.
Since ##c##, the speed of light, remains constant, as frequency goes up, wavelength must go down.
Therefore violet has the highest frequency and the shortest wavelength of the visible colors of light.
And red has the lowest frequency and the longest wavelength of the visible colors of light.