A chessboard on which the chess pieces are not only black and white but are also shades of grey.
The idea of the cartoon is that conflict occurs when things are seen in black and white or when people are polarised in outlook. With shades of gray or nuances of opinion conflict is less likely – specifically as on the chessboard in the illustration.
This is not a metaphor about race or racial prejudice, although metaphorical links can be made.
The cartoon is a comment on the fact that people tend to analyse things in black and white, as “either/or” or in binary.