The color with the highest frequency in the visible spectrum is
violet.
In terms of light, frequency is directly related to the color's position in the electromagnetic spectrum. Violet light has a frequency of about
670–790 THz (terahertz), which is the highest frequency range in the visible light spectrum.
To give you an idea, as the frequency of light increases, the color shifts towards the violet end of the spectrum, while lower frequencies correspond to colors like red.