Have you been swimming?- Chlorine will change the colour of your hair extensions, it will also cause damage and matting. If possible avoid swimmimg underwater. Tie hair up in a high bun to protect it from the chlorine. Blonde hair especially can turn pink/orange or have a green tinge. It may be possible to reverse this with a toner or shampoo but sometimes such damage cannot be repaired. Sunshine and UV rays can cause your hair extensions to change colour, it can lighten them