Why isnt this defaulting to red?

HTML-CSS
#1

Tell us what’s happening:

Your code so far


<style>
  :root {
    --red-color: red,red;
  }
  .red-box {
    
    background: var(--red-color, red);
    height: 200px;
    width:200px;
  }
</style>
<div class="red-box"></div>
#2

You need to understand CSS Variables better. You have a mistake in your variable declaration. Please read and test all the examples from MDN official documentation or solve again all the challenges from freeCodeCamp that contain “CSS Variables”.
Basic CSS - Learn freeCodeCamp
Using CSS custom properties - MDN

#3

Should be:

[spoiler]```

:root { --red-color: red; } .red-box { background: var(--red-color); height: 200px; width:200px; }
```[/spoiler]
#4