What does PaintStyle.fillColor of AxisGuide.grid use for?

[KrahmalK]

I set strokeColor and strokeWidth and they are like splitLine in EChart.
And now I want to set something like splitArea in EChart:

areaStyle: {
    color: [
          color1,
          color2
    ]
}

but these do not work:

grid: PaintStyle(
   fillColor: color1,
),

I can only set the background color in coord:

coord: RectCoord(
   color: color1,
),

Can anyone help me resolve this multi-color areaStyle? Thanks.