Second, because oil will hinder coloring, it is best to wash your hair the night before dyeing, and color directly the next day without washing your hair. Then it is best not to wash your hair for three days. Of course, it doesn't matter if you really can't stand hair oil.
Thirdly, color care products can only prolong the residence time of hair color by reducing the oxidation reaction of hair dye, and can't really solve the problem of color fading. Generally speaking, the durability of Swarovski household hair cream is 2~3 months in brown and 1~2 months in red, which varies according to everyone's hair quality and washing habits (and it should be noted that not only washing hair, but also ultraviolet rays are the main reasons for fading).
Fourth, it's hard to say. My personal experience is to avoid colors that are easy to fade (red and purple, in fact, blue and light colors are also easy to fade, but Schwartz's household hair dye cream is not as good as those two colors), maintain your hair, make a hair mask regularly, and don't wash your hair with overheated water. Try to avoid using dandruff shampoo after dyeing your hair.