Why are my plastics discolored?
Pink/orange discoloration of plastics is usually caused by carotenoid, a class of typically red/orange pigments found in foods such as tomatoes and turmeric. When carotenoids are dissolved in oils, they become easily absorbed into many plastics, mainly when heat is also applied. Because the resulting stain is absorbed into the plastic, water-based bleaches are ineffective.
Are the items being rinsed?
Pre-rinsing or using a Rinse Hold cycle will reduce the chance of staining. Regular use of a rinse cycle and an air-dry or energy-saving dry option will reduce the likelihood of staining.
How to remove it?
Try using a commercial plastic cleaner. If unable to find a commercial plastic cleaner, carotenoid stains can be bleached by ultra-violet light. If possible, allow sunlight to shine on the item, and the stain will fade. This process is slow and may take a long time to achieve the desired results.