Check out example codes for "bootstrap border color". It will help you in understanding the concepts better.

Code Example 1

<span class="border border-primary"></span>
<span class="border border-secondary"></span>
<span class="border border-success"></span>
<span class="border border-danger"></span>
<span class="border border-warning"></span>
<span class="border border-info"></span>
<span class="border border-light"></span>
<span class="border border-dark"></span>
<span class="border border-white"></span>

Code Example 2

Border-radius
Add classes to an element to easily round its corners.

<img src="..." alt="..." class="rounded">
<img src="..." alt="..." class="rounded-top">
<img src="..." alt="..." class="rounded-right">
<img src="..." alt="..." class="rounded-bottom">
<img src="..." alt="..." class="rounded-left">
<img src="..." alt="..." class="rounded-circle">
<img src="..." alt="..." class="rounded-0">

Code Example 3

<span class="border"></span>
<span class="border-top"></span>
<span class="border-right"></span>
<span class="border-bottom"></span>
<span class="border-left"></span>

Code Example 4

<span class="border">Text</span>
<span class="border-top">Text</span>
<span class="border-right">Text</span>
<span class="border-bottom">Text</span>
<span class="border-left">Text</span>

Code Example 5

<span class="border-0"></span>
<span class="border-top-0"></span>
<span class="border-right-0"></span>
<span class="border-bottom-0"></span>
<span class="border-left-0"></span>

Learn ReactJs, React Native from akashmittal.com