Whether the hair color of pitaya will fade after one month depends on many factors. Generally speaking, pitaya can be dyed for about a month, but the specific duration may vary from person to person. The following factors may affect the dyeing effect:

1. quality of hair dye: different brands of hair dye may be different, and poor quality hair dye may fade faster.

2. Post-dyeing care: If you wash your hair frequently or blow your hair with hot air after dyeing, it may accelerate the fading.

3. Natural factors: Outdoor activities such as ultraviolet irradiation and swimming may make the color fade gradually.

In short, the hair dyeing of pitaya can last for about a month in general, but the specific duration will vary from person to person. If you want to maintain the dyeing effect, it is recommended to avoid frequent shampoo and hot air blowing, and pay attention to sun protection to keep your hair dry. If the color fades, you can consider re-dyeing your hair or using professional color protection products to prolong the dyeing effect.