Clear elastic ties stay clear the longest if you avoid the following foods, drinks and spices:
Turmeric, curry, Indian food in general, beetroot juice, cherries, tomatoes, lyutenitsa (Bulgarian pepper relish) and ketchup, coffee, cigarettes, chocolate drinks, Coca-Cola and any drinks with artificial colourings. After eating a staining food or having a staining drink, it's a good idea to rinse the colourings away with water straight away and, if possible, to brush your teeth 40 minutes after eating. You can drink coloured drinks through a straw and take frequent sips of water.
This answer is for general information. Your own case needs an examination by an orthodontist.