I really like the link you provided and have watched it before!

But - I do want to say that C == green is not arbitrary at all. It is consistent with my calculations, which are consistent with Newton's calculations. Usually I see the colours being assigned to notes as wrong.. but this C == green is consistent with mapping light, using octave equivalence, given by the following:

  f_prime = f * 2 ** (i / 12)
  # Where, 
  # f' is the derived f, (in this case Green {5.66 × 10^14 Hz})
  # f is the reference f (in this case 261.63 Hz)
  # i is the interval in semitones

Let's say that C == 261.63 Hz, and that Green == 5.66 × 10^14 Hz. Using the preceding formula we can make a small (python) program to check whether C == Green.

  light_range_min = 400 * 10 ** 9 # Hz
  light_range_max = 790 * 10 ** 9 # Hz
  C = 261.63 # Hz
  octave = 0
  for octave in range(100): # we are just using a high number here
      f_prime = C * 2 ** (12 * octave / 12)
      if f_prime >= light_range_min:
          octave = octave
          break
  print(f"C in the range of light has f == {f_prime}, which is {f_prime / 10 ** 9} THz. We had to go {octave} octaves up to arrive there")
  # outputs: C in the range of light has f == 561846146826.24, which is 561.84614682624 THz. We had to go 31 octaves up to arrive there

We can look up colour charts like [0] or [1] and find that this frequency is in fact associated with the colour green.

The rest of your commentary seems valid.

[0] https://en.wikipedia.org/wiki/Visible_spectrum

[1] https://sciencestruck.com/color-spectrum-chart