.grijs {
  background-color: lightblue;
}

.beide {
  border-style: none solid none solid; 
  border-width: 0px;
}

.linkss {
  border-left-style: solid; 
  border-width: 0px;
}

.rechts {
  border-right-style: solid; 
  border-width: 0px;
}