Add those line into your settings.json file
"workbench.colorCustomizations": {
"diffEditor.removedTextBackground": "#FF000055",
"diffEditor.insertedTextBackground": "#00ff0055",
"diffEditor.insertedTextBorder": "#00000000",
"diffEditor.insertedLineBackground": "#00ff0055",
"diffEditor.diagonalFill": "#FFFFFF55",