What does it mean to cover the grave with red cloth?

The red cloth on the grave represents the red grave;

The custom of the red grave comes from a legend. It is said that when the ancients saw the death of minors, they painted the graves red to remind them that the black-and-white impermanence of haunted houses was minors, so that when the black-and-white impermanence sent the souls of the deceased to Naiheqiao, they were released and reincarnated without interrogation and torture in hell. In short, this is the memory and prayer of parents for their dead children.

Extended data:

It is a common custom of ethnic minorities in the mountainous areas of southwest China (eastern and northern Guizhou, southwestern Sichuan and northern Yunnan) and northwest (central Gansu and eastern Qinghai). Mainly used for the burial of minors and pregnant women or girls, the graves of the deceased are generally painted red or dark red.

For example, pigs are bloody, but in some areas, such as Guizhou, Gansu and Sichuan, the burial method of red graves is that relatives personally cover the coffin with a red cloth when carrying the coffin. After burial, the red cloth should stay at the grave tip for at least 5 days, and then be picked up and burned by relatives.