The way that this is put together make it not obvious that this is all one giant list comprehension.

Sugested change:
```Python
 65     color_arg = [mcols.colorConverter.to_rgba(colour) for 
 66                  colour in (colour_min, colour_zero_minus or colour_zero,
 67                             colour_zero, colour_zero_plus or colour_zero,
 68                             colour_max)]
 69     (colour_min, colour_zero_minus, colour_zero, colour_zero_plus,
 70      colour_max) = color_arg
```

Splitting after the `for` makes it much easier to read IMO