An array of arrays of hexadecimal color strings from the “Greys” sequential color scheme. The kth element of this array contains
the color scheme of size k; for example, d3.schemeGreys[9] contains an array of nine strings representing the nine colors of the
grey sequential color scheme. Sequential, single-hue color schemes support a size k ranging from 3 to 9.
An array of arrays of hexadecimal color strings from the “Greys” sequential color scheme. The kth element of this array contains the color scheme of size k; for example, d3.schemeGreys[9] contains an array of nine strings representing the nine colors of the grey sequential color scheme. Sequential, single-hue color schemes support a size k ranging from 3 to 9.