On Blender 3.4.1, after applying a geometry nodes modifier with a set vertex color to a curve, you can display that curve with flat vertex color on the Solid > Flat > Attribute.
However, from blender 3.5 and upwards, it doesn’t displays vertex color applied to curves anymore, instead it only shows black.
One way to display it, is on the Viewport shading > Material Preview by connecting the Color Attribute to the Base Color input of a material, but this displays the vextex color on a lit condition, and doesn’t looks flat.
This is the geometry nodes setup that was used to apply vertex color to curves back in blender 3.4.1
I would like this feature back to visualize a character’s hair color with a flat shaded look, using editable curves and without having to convert curves into mesh.