use d3.color('rgba(255,255,255,0)'), the rgb is all NaN. about d3-color

[mbostock]

That looks like a bug in #67.

[mbostock]

The color parser treats transparent colors as having undefined R, G and B values because CSS does not support an explicit way of representing undefined channel values and therefore supporting achromatic interpolation. If you want to construct a transparent color with defined R, G and B values, you need to use the d3.rgb constructor instead:

d3.rgb(255, 255, 255, 0)

[nickofthyme]

Is this intentionally different functionality for hexadecimal colors?

d3.rgb('#00000000)');

// returns
{
  r: 0,
  b: 0,
  g: 0,
  opacity: 0,
}

[mbostock]

Fixed in f176ff1.