Attribute from color

I have these three boxes that I would like to have a vertex color gradient across.

With these nodes below I was able to get a ordered vertex across.

SORT node
Point Sort: By X ( I started by sorting the vertex numbers by a direction/vector. This helps the coloring/values later on )

Enumerate node
Group type = Points
Attribute = _ptnum

Color node
Color Type : Ramp from Attributes
Attribute: _ptnum
Range: 0 to ( Max numbers you can see. I'm sure there is a way to gather this number)

// AttribWrangle 
// Preset Grow Hair in Attribute wrangle
// In this instance I was using a 0-1 color grad to determined the length of the hairs by dividing a random length * @Cd

        // THE USE OF A COLOR HERE TO DETERMIND HAIR LENGTH
        pos += dir * (len * @Cd) / steps;