div
{
  height: 100px;
  width: 100px;
  border-radius: 50%;
  margin:auto;
  margin-bottom:10px;
}
body
{
 background: black; 
}
#redBox
{
background: red;  
}
#orangeBox
{
background: orange;
}
#yellowBox
{
background: yellow;
}
#greenBox
{
background: green;
}

#blueBox
{
background: blue;
}

#violetBox
{
background: violet;
}