HTML

change color of mark in css

<style>
  h1 mark {
    background-color: cyan (add any color you want);
  }
</style>
<h1>
  <mark>
    And Voila! Cyan highlights!
  </mark>
</h1>

css mark color

<style>
mark { 
  background-color: yellow;
  color: black;
}
</style>

<mark>Highlighted text!!</mark>