Get your hair completely wet before applying the shampoo. Warm water is both soothing and healing to your hair. The temperature helps expand your hair shafts and allow them to better absorb the purple shampoo. Apply the purple shampoo to your hair from root to tip. Massage the shampoo in gently as you work the shampoo through your hair, lathering the shampoo in as you go. Pay special attention to hit your hair's "problem areas"—brassy or yellowed strands that you're hoping to treat with the shampoo.  If you're using purple shampoo on highlights, only apply the shampoo to blond streaks. Purple shampoo does not affect dark hair. Prioritize your roots while shampooing to prevent damaged hair in the future. If your hair is a warmer, natural blonde color and has mild brassiness, 2-3 minutes should be enough time. After several minutes have passed, rinse your hair out with cool water.  Your roots will need more time to absorb the shampoo than your ends, which is why you apply the shampoo there first. Ends are more porous and change tones easily. The recommended time may vary slightly from brand to brand. The shampoo may need to be left on for up to 5 mins. If your hair is significantly discolored or you have recently dyed your hair blonde, leave the shampoo in for 5 to 15 minutes. Your hair may need more time to fully absorb the tone. Then, wash the shampoo out of your hair with cool water.  If you have never used purple shampoo before, try leaving it in for 5-10 minutes and washing it off. If you notice little or no difference in color after drying your hair, try 10-15 minutes for your next treatment. If you leave the shampoo on longer than 15 minutes, expect lilac tinting to be left in your hair. While this could work for gray or silver hair, your natural blonde look could be ruined. Although individuals with darker hair may worry about draining their hair of color, silver and platinum benefits from leaving the shampoo in longer. Keep the shampoo in your hair for up to half an hour before rinsing, depending on...

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Write a summary of the previous text in Vietnamese:
Làm ướt tóc bằng nước hơi âm ấm. Xoa dầu gội vào tóc. Để dầu gội lưu trên tóc khoảng 2-3 phút nếu bạn có tóc vàng tự nhiên. Để dầu gội trên tóc đến 15 phút với mái tóc ngả màu đồng thau hoặc tóc nhuộm. Để dầu gội trên tóc 30 phút đối với tóc màu xám, màu bạc hoặc bạch kim. Dùng dầu xả như thường lệ sau khi xả sạch dầu gội.