io_mesh_atomic: atom objects had no 'diffuse_color'

Property 'material.diffuse_color' is now set such that one can see the
color of the atoms in also the 'Solid mode' of the Viewport.

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io_mesh_atomic/pdb_import.py

@@ -1343,6 +1343,7 @@ def import_pdb(Ball_type,
     # (e.g. hydrogen)
     for atom_type in atom_all_types_list:
         material = bpy.data.materials.new(atom_type[1])
+        material.diffuse_color = atom_type[2]
         material.use_nodes = True
         mat_P_BSDF = material.node_tree.nodes['Principled BSDF']
         mat_P_BSDF.inputs['Base Color'].default_value = atom_type[2]

io_mesh_atomic/xyz_import.py

@@ -486,6 +486,7 @@ def import_xyz(Ball_type,
         # Take the first atom
         atom = atoms_of_one_type[0]
         material = bpy.data.materials.new(atom.name)
+        material.diffuse_color = atom.color
         material.use_nodes = True
         mat_P_BSDF = material.node_tree.nodes['Principled BSDF']
         mat_P_BSDF.inputs['Base Color'].default_value = atom.color