source/blender/blenkernel/BKE_instances.hh

@@ -103,7 +103,8 @@ class Instances {
   mutable blender::Array<int> almost_unique_ids_;
 
   CustomDataAttributes attributes_;
-
+  std::string default_color_attribute_;
+  std::string active_color_attribute_;
  public:
   Instances() = default;
   Instances(const Instances &other);
@@ -176,6 +177,10 @@ class Instances {
 
   bool owns_direct_data() const;
   void ensure_owns_direct_data();
+
+  void set_color_attribute_metadata(const char *default_color_attribute, const char *active_color_attribute);
+  const std::string &default_color_attribute_name() const { return default_color_attribute_; }
+  const std::string &active_color_attribute_name() const { return active_color_attribute_; }
 };
 
 /* -------------------------------------------------------------------- */

source/blender/blenkernel/intern/instances.cc

@@ -330,4 +330,14 @@ Span<int> Instances::almost_unique_ids() const
   return almost_unique_ids_;
 }
 
+void Instances::set_color_attribute_metadata(const char *default_color_attribute, const char *active_color_attribute)
+{
+  if (default_color_attribute) {
+    default_color_attribute_ = default_color_attribute;
+  }
+  if (active_color_attribute) {
+    active_color_attribute_ = active_color_attribute;
+  }
+}
+
 }  // namespace blender::bke

source/blender/geometry/intern/realize_instances.cc

@@ -206,6 +206,8 @@ struct AllMeshesInfo {
   /** True if we know that there are no loose edges in any of the input meshes. */
   bool no_loose_edges_hint = false;
   bool no_loose_verts_hint = false;
+  char const *active_color_attribute = nullptr;
+  char const *default_color_attribute = nullptr;
 };
 
 struct AllCurvesInfo {
@@ -902,6 +904,13 @@ static AllMeshesInfo preprocess_meshes(const bke::GeometrySet &geometry_set,
         info.materials.add(material);
       }
     }
+    if (info.default_color_attribute == nullptr) {
+      info.default_color_attribute = mesh->default_color_attribute;
+    }
+    if (info.active_color_attribute == nullptr) {
+      info.active_color_attribute = mesh->active_color_attribute;
+    }
+
   }
   info.create_material_index_attribute |= info.materials.size() > 1;
   info.realize_info.reinitialize(info.order.size());
@@ -1558,6 +1567,23 @@ bke::GeometrySet realize_instances(bke::GeometrySet geometry_set,
     new_geometry_set.add(*gather_info.r_tasks.first_edit_data);
   }
 
+  if (new_geometry_set.has_mesh())
+  {
+    Mesh *dst_mesh = new_geometry_set.get_mesh_for_write();
+
+    /* Get the default color attribute from the instance domain, this
+     * corresponds to the default specified on the instancer. */
+    const std::string &default_color_attribute = geometry_set.get_instances_for_read()->default_color_attribute_name();
+    if (default_color_attribute.size()) {
+      BKE_id_attributes_default_color_set(&dst_mesh->id, default_color_attribute.c_str());
+    }
+
+    const std::string &active_color_attribute = geometry_set.get_instances_for_read()->active_color_attribute_name();
+    if (active_color_attribute.size()) {
+      BKE_id_attributes_active_color_set(&dst_mesh->id, active_color_attribute.c_str());
+    }
+  }
+
   return new_geometry_set;
 }
 

source/blender/nodes/geometry/nodes/node_geo_instance_on_points.cc

@@ -15,6 +15,8 @@
 #include "BKE_attribute_math.hh"
 #include "BKE_instances.hh"
 
+#include "DNA_mesh_types.h"
+
 #include "node_geometry_util.hh"
 
 namespace blender::nodes::node_geo_instance_on_points_cc {
@@ -218,6 +220,10 @@ static void node_geo_exec(GeoNodeExecParams params)
                                      instance,
                                      params,
                                      attributes_to_propagate);
+        if (type == GeometryComponent::Type::Mesh) {
+          const Mesh *src_mesh = geometry_set.get_mesh_for_read();
+          dst_instances->set_color_attribute_metadata(src_mesh->default_color_attribute, src_mesh->active_color_attribute);
+        }
       }
     }
     geometry_set.remove_geometry_during_modify();