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

Code Example 1

p
{

   
text-decoration: underline;
 
text-decoration-color: red;

}

Code Example 2

u
{
	text-decoration: underline;
  	text-decoration-color: red;
}
example of use: (in html)

<p>The word <u>CAT</u>, is underlined </p>

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