CSS selector for first element with class

Question

I have a bunch of elements with a class name red, but I can't seem to select the first element with the class="red" using the following CSS rule:

.red:first-child {
    border: 5px solid red;
}

<p class="red"></p>
<div class="red"></div>

What is wrong in this selector and how do I correct it?

Thanks to the comments, I figured out that the element has to be the first child of its parent to get selected which is not the case that I have. I have the following structure, and this rule fails as mentioned in the comments:

.home .red:first-child {
    border: 1px solid red;
}

<div class="home">
    <span>blah</span>
    <p class="red">first</p>
    <p class="red">second</p>
    <p class="red">third</p>
    <p class="red">fourth</p>
</div>

How can I target the first child with class red?

Answer 1

The correct answer is:

.red:first-child, :not(.red) + .red { border:5px solid red }

Part I: If element is first to its parent and has class "red", it shall get border.
Part II: If ".red" element is not first to its parent, but is immediately following an element without class ".red", it shall also deserve the honor of said border.

Fiddle or it didn't happen.

Philip Daubmeier's answer, while accepted, is not correct - see attached fiddle.
BoltClock's answer would work, but unnecessarily defines and overwrites styles
(particularly an issue where it otherwise would inherit a different border - you don't want to declare other to border:none)

EDIT: In the event that you have "red" following non-red several times, each "first" red will get the border. To prevent that, one would need to use BoltClock's answer. See fiddle

Answer 2

you could use first-of-type or nth-of-type(1)

.red {
  color: green;  
}

/* .red:nth-of-type(1) */
.red:first-of-type {
  color: red;  
}

<div class="home">
  <span>blah</span>
  <p class="red">first</p>
  <p class="red">second</p>
  <p class="red">third</p>
  <p class="red">fourth</p>
</div>

Answer 3

The above answers are too complex.

.class:first-of-type { }

This will select the first-type of class. MDN Source

Answer 4

For some reason none of the above answers seemed to be addressing the case of the real first and only first child of the parent.

#element_id > .class_name:first-child

All the above answers will fail if you want to apply the style to only the first class child within this code.

<aside id="element_id">
  Content
  <div class="class_name">First content that need to be styled</div>
  <div class="class_name">
    Second content that don't need to be styled
    <div>
      <div>
        <div class="class_name">deep content - no style</div>
        <div class="class_name">deep content - no style</div>
        <div>
          <div class="class_name">deep content - no style</div>
        </div>
      </div>
    </div>
  </div>
</aside>

Answer 5

Try this solution:

 .home p:first-of-type {
  border:5px solid red;
  width:100%;
  display:block;
}

<div class="home">
  <span>blah</span>
  <p class="red">first</p>
  <p class="red">second</p>
  <p class="red">third</p>
  <p class="red">fourth</p>
</div>

CodePen link

Answer 6

To match your selector, the element must have a class name of red and must be the first child of its parent.

<div>
    <span class="red"> <!-- MATCH -->
</div>

<div>
    <span>Blah</span>
    <p class="red"> <!-- NO MATCH -->
</div>

<div>
    <span>Blah</span>
    <div><p class="red"></div> <!-- MATCH -->
</div>