I think Mr Amanjit said his Mother (who was a laundress) put Indigo in her laundry to make it look white.
This from a site about Reckitt & Colman
Stone blue, fig blue, blue starch - indigo & smalt
Before factory-made chemicals were available, clothes were whitened with blue derived from indigo, or from powdered blue smalt: ground glass containing cobalt. The indigo was processed, mixed with starch, and sometimes other additives, and formed into lumps. This was stone blue, or fig blue, or thumb blue. Other names which have been used for bluing whiteners include Mecklenburg blue and Queen's blue. Prussian blue, still an ingredient in a modern bluing liquid, was discovered in the early 18th century, and used on laundry long before synthetic ultramarine
I don't think you would have added Iodine to the laundry as it is an incredibly deep purple when in the bottle.Not only that but it would be almost impossible to remove from clothes.