Reply To: Piero: Cycles Hair Shape Settings in Blender 2.90

@bkol The “From Instancer” box must be checked only if you use the hairs for duplicating objects and it works only with Cycles. Hair strands alone automatically pick the color from the lacation where they are growing. The black lines in the example file here also appear when using a “Transparent BSDF Node” instead of the “Principled Node”  if the angle between the transparent plane and the intransparent cube of that file is very small: