Geometry Nodes Vertex Colors

Have the geometry nodes actually write to the vertices, instead of just to an attribute. Using attributes and the Attribute node to access vertex colors in a shader inside of Blender is all well and good, but should you apply the modifier or attempt to export the mesh there's no vertex colors actually written in the mesh, meaning you can't use Geo Nodes to generate any useful masks or bake offsets etc for use in other tools.

It also means you can neither preview them in viewport or use the Vertex Color node to access them in shader nodes.