How do I map a list of values to specified colors?

[larkypython]

Here is what I want to do:
a list of 19 values:
[-1, 1, -2, 2, -3, 3, -4, 4, -5, 5, -6, 6, -7, 7, -8, 8, -9, 9, 0]
I would like the color grey gradual from white to black in the order in the list. How can I do that?
or else, if I can specify each different color to each different values, that is also ok.

Thanks.