Mine usually only take 30-40 mins, topping the water up every 5-10 mins, but I use black mostly.
Since your not boiling over a stove it won't harm you to keep them in longer, especially with it being a lighter colour.
If the water goes cold the dye won't penetrate the plastic, so make sure you keep as hot as possible with the kettle
Since your not boiling over a stove it won't harm you to keep them in longer, especially with it being a lighter colour.
If the water goes cold the dye won't penetrate the plastic, so make sure you keep as hot as possible with the kettle