<button style="background-color: black; color: white;" onmouseover="this.style.backgroundColor='yellow'; this.style.color='navy';" onmouseout="this.style.backgroundColor='black'; this.style.color='white';">Button 1</button>
<button style="background-color: black; color: white;" onmouseover="this.style.backgroundColor='yellow'; this.style.color='navy';" onmouseout="this.style.backgroundColor='black'; this.style.color='white';">Button 2</button>
<button style="background-color: black; color: white;" onmouseover="this.style.backgroundColor='yellow'; this.style.color='navy';" onmouseout="this.style.backgroundColor='black'; this.style.color='white';">Button 3</button>
<button style="background-color: black; color: white;" onmouseover="this.style.backgroundColor='yellow'; this.style.color='navy';" onmouseout="this.style.backgroundColor='black'; this.style.color='white';">Button 4</button>
<button style="background-color: black; color: white;" onmouseover="this.style.backgroundColor='yellow'; this.style.color='navy';" onmouseout="this.style.backgroundColor='black'; this.style.color='white';">Button 5</button>

.renk-degis {
  background-color: black;
  color: white;
}

.renk-degis:hover {
  background-color: blue;
  color: yellow;
}