style.css

*{
  padding: 0;
  margin: 0;
  box-sizing: border-box;
}

body{
  background: #333;
  text-align: center;
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

.header{
  background-color: slateblue;
  color: white;
  margin: 0;
  padding: 0;
  transition: .9s;
}
.header *{
  padding: 10px;
}

.mode{
  background-color: #fff;
  display: flex;
  justify-content: space-between;
  padding:0 30%;
  align-items: center;
  font-size: 12px;

}

.mode span:hover{
  background-color: #673AB7;
  color: white;
}

.diff{
  display: flex;
}
.diff *{
  margin-left:20px;
  transition: 0.5s;
}

.diff span:hover{
  background: #673AB7;
  color: white;
}

.colors{
  height: 200px;
  width: 280px;
  background-color: #333;
  margin: 10px auto 5px auto;
  padding: 10px 10px;
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  align-items: center;
}

.colors div{
  height: 80px;
  width: 80px;
  background:teal;
  border-radius: 8px;
  /* transition: .4s; */
}

.colors~p{
  margin-top: 0;
  text-transform: uppercase;
  color: white;
  transition: 0.4s;
  font-size: 12px;
  font-weight: bold;
}

#reset{
  background-color: green;
  color: white;
  border-style: hidden;
  border-radius: 3px;
  width: 90px;
  height: 27px;
  margin-top: 10px;
  display: none;
}