body.gray {
  background: #e7e7e7;
  color: white;
}
body.white {
  background: white;
  color: black;
}
body.red {
  background: red;
  color: white;
}
body.yellow {
  background: yellow;
  color: black;
}

#grayButton {
  background: #e7e7e7;
}
#whiteButton {
  background: white;
}
#redButton {
  background: red;
}
#yellowButton {
  background: yellow;
}