While the sun can burn and tan (i.e. darken) your skin, it's also lighten your hair.  One of the easiest ways to lighten your hair is to simply spend a lot of time outside in the sun.  Always remember to wear sunscreen and protective clothing on your exposed skin so you don't get sun damage. The great thing about the sun is that it can be used on its own, or in combination with any of the other hair lightening treatments.  To have the sun lighten your hair faster, apply one of the mixtures mentioned in this article to your hair first, before going outside. To lighten your hair with vitamin C, you'll need to obtain vitamin C tablets or pills.  Crush 8-9 of your vitamin C tablets into a powder and then add the powder to your regular shampoo.  Use your shampoo normally and the added vitamin C will slowly lighten your hair. As an alternative you can make a hair mask with vitamin C.  Take 15-20 vitamin C tablets and crush them into a powder.  Then add the powder to a small amount of anti-dandruff shampoo to form a paste.  Apply the paste all over your hair.  Put on a shower cap or plastic wrap and leave the mixture on for 1-2 hours, then rinse off with water. If you have tried other lightening options and you haven't found them to work, or they do not last long enough to satisfy you, you may want to consider a more professional option.  Also, if you have dark hair and want a more dramatic lightening effect, or if you have previously colored your hair at home or at a salon, then you will need to see a professional hair stylist. Professional hair color products are not made equal.  There are several hair color products that are made without bleach or hydrogen peroxide, and even without other harmful chemicals.  Because each person's hair is different, your best option is to make an appointment with your hair stylist or colorist and ask them for the best non-bleach option.

TL;DR in Vietnamese:
Tận dụng ánh nắng để làm sáng màu tóc một cách tự nhiên. Thử dùng vitamin C làm sáng màu tóc. Cân nhắc sản phẩm làm sáng màu tóc.