Once you have rinsed your panties with clear water, you can then put them in the washing machine in a delicate cycle at 30°C with your other clothes: no risk of staining! Do not use fabric softener.
Or, hand wash
If you do not have a washing machine, use a non-greasy soap to clean it with warm water.
Dry your panties in the open air. Do not use a tumble dryer, hair dryer, radiator or iron.