How to play the timbre of guitar well?

It means that the angle of your pick is not vertical when touching the string, or the pick touches the string too deeply. Pay attention to touch the plane of the strings, and try to be vertical. This sound may be caused by one side of your pick rubbing against the strings. In addition, playing different things may require different usage of pick, so don't stick to it. The voice of "Chen Wenjing" is not necessarily a bad voice, but sometimes it may be needed by the effect.