Chromosphereic Radioisotope Seeding
It would probably be cheaper and easier, as well as visible over longer distances, to dump short-lived radioisotopes into stars, which would give spectral evidence for intelligent life since these materials are not naturally found in stellar atmospheres.
When Technetium was first discovered in some stellar spectra, it was seriously proposed that this was what was happening, until a natural mechanism for its presence was identified.