If your curtains are shaded or white and do not really fit nicely with new wall color or interior décor, NO problem. Make very strong black tea.
For example: 10 tea bags per 2 gallons of water. Put your curtains in that tea and leave them in for a few minutes, then rinse. If fabric softener is used, the whole house will smell nicely. Just remember: stronger tea – darker “off white” color.