One principle that has been tried is to take the bass frequency i.e. 41hz and keep doubling it until you get into the light frequency range then see what corresponds.
= 704,374,636,544 = 704 ThZ or Violet
A = 55 Hz
so, 472,446,402,560 Hz is its corresponding Red
D = 73 Hz, corresponding to 627 ThZ or Blue
G = 98 Hz, the problem child
it's either 841 ThZ, which is over the range for colors
or 421 ThZ, which is under the range
).