Plastic can absorb Stains, so you will need to use some kind of bleaching poduct.
some products you can try individually:
- Baking soda
- Bleach
- Water
- Vinegar
- Rubbing alcohol
Dilute with luke warm water , except for Rubbing Alcohol
Use some kind of tray which you don't mind if it gets bleach stains to protect your countertop. put the device on the tray.
If you can't soak an item, try disconnecting the device, then wrapping a lightly soaked hand towel or paper towel over the area that is discolored
Rinse with luke warm water, and make sure device has completely dried before reconnecting.