How can I change the hover effect color?

How can I get the color of a link to change when a mouse is hovered over it? 

If you're referring to this background color shown in the image below:

You can change it by adding custom CSS code. Here's the custom CSS code:

.form-line-error { 

    background-color: #464646 !important; 

} 

You can change the hex color code to your own preferences. For more hex color code, please check this link: http://www.color-hex.com/

Here's a guide on: How-to-Inject-Custom-CSS-Codes

Result:

If you have questions, please contact us again. Thank you.

No. Im talking about the text, when you put a link on the text. I want the text/link to turn a different color when the mouse hovers over. 

Hello,

To my understanding, you want to write a URL inside the text field and you want to change its color when you hover on it as seen below:

You can inject the following CSS code in order to change its color when hovering on it as you can see in the following screencast below:

a:hover {

    color: hotpink;

}

Please try and if you need further assistance, let us know.

Thanks.

Does the same CSS code work if I want to write the words "click here" inside a textfield and hyperlink the "click here" to redirect them to a different page? 

Hello,

Yes, the same CSS code will work as you can see the screencast below:

Please try and if you need any further assistance, let us know.

Thank you.