CSS - Cor

Fundo

<!-- index.html -->
<!-- Head starts -->
<style>
  .silver-background {
    background-color: silver;
  }

  .square {
    width: 200px;
    height: 200px;
  }
</style>
<!-- Style block end -->
<!-- Head ends -->
<!-- Body starts -->
<div class="silver-background square"></div>
<!-- Body ends -->

Sobrescrever

<!-- index.html -->
<!-- Head starts -->
<style>
  .blue-text {
    color: blue;
  }

  .red-text {
    color: red;
  }

  .orange-text {
    color: orange;
  }
</style>
<!-- Style block end -->
<!-- Head ends -->
<!-- Body starts -->
<p class="blue-text">Blue</p>
<p class="blue-text red-text">Blue</p>
<p class="blue-text red-text orange-text">Orange</p>
<!-- Body ends -->

RGB

<!-- index.html -->
<!-- Head starts -->
<style>
  .rgb-background {
    background-color: rgb(0, 0, 0);
  }

  .square {
    width: 200px;
    height: 200px;
  }
</style>
<!-- Style block end -->
<!-- Head ends -->
<!-- Body starts -->
<div class="rgb-background square"></div>
<!-- Body ends -->