I'm going to start by showing you how to highlight specific words in a paragraph, and then move on to highlighting a whole paragraph.

Step 1:
Go to the text editor of the specific post or page you want to modify, and find the word you wish to highlight.
I chose the word "never":

Step 2:
We will now embed the specific word that we have chosen, inside of a span tag that looks like this <span>...............</span>.
We do that, to separate the specific word from the rest of the text and to be able to give it the styling that we desire.

Step 3:

Now, if I want to highlight the word "never" with, lets say red, I have to include this code in my opening tag: style="background-color: red;"

, so my code will now look like this:

If i wish to use another color, for example a nuance of red that doesn't have a name, I will use the hexadecimal code of that nuance.
And here is where the color picker comes in. You can replace the word "red" with a hexadecimal code, so your code will look like this:

On the Next page I will show you how to highlight a paragraph.