Hello FB,
There is a comment in the script which says:
// colorBlend will return a color when the index is between min and max and white when it is less than min.
// To see black when it is more than max, uncomment the last line of colorBlend.
// The min/max values were computed automatically and may be poorly specified, feel free to change them to tweak the displayed range.
For example setting min and max to -1.3 and 0.0 yields some results.
Hope it helps!
Kind regards,
Anze