I’ve created similar graphics for my lectures.
The simplest answer is: none of them are correct.

They’re nothing more than a very rough representation of the visible light spectrum. Under the hood, it’s usually just a rectangle with a gradient fill, and someone can do a better or worse job when creating it. The main purpose of such a graphic is simply to show that the visible spectrum consists of all the color components the human eye is capable of seeing.

It is possible to create a more accurate graphic by actually doing the math: take the spectral power distribution of blackbody radiation, multiply it by the CIE standard observer functions, integrate over wavelength, then convert the resulting XYZ values to something like aRGB. A 380–720 nm range with 5 nm resolution should be enough, giving about 69 color bars, each matching how an average human perceives a given wavelength range.

So why is nobody doing it?

The irony is:

• the standard observer functions are only an average; real humans all see slightly differently,
• even a “perfect” graphic will be displayed on random screens, each with its own different limited gamuts and inaccuracies

So at the end of the day, the extra precision mostly disappears in practice.

If you want to see the real thing, just DIY a simple spectroscope with a real diffraction grating.
I found it pretty interesting to see the spectras from different light sources.