CSS - Change text color depending on background

Question

I have a simple layout consisting of three full height divs and a fixed header bar.

Answer 1

You can use mix-blend-mode:difference

body,
html {
  padding: 0;
  margin: 0;
}

.header {
  position: fixed;
  width: 100%;
  height: 50px;
  margin: 20px;
  color:#fff;
  mix-blend-mode: difference;
}

.section1,
.section2,
.section3{
  background: black;
  height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
}

.section2 {
  background: white;
  color:#000;
}

  Header Content


  

    Section One Content
  
  

    Section Two Content
  
  

    Section Three Content