How to remove background colour on when hovering over a button

I cant seem to remove the standard colored background upon hover of a button. I can change the color of the background but not get rid of it completely. Id like to have the text appear color #A, then when hovered upon the text colour changes to #B but without a background. 

The email address is the link and I want it to appear as is on the page, but when hovered, it to have no background and just change to a darker colour.

Please provide url.

https://www.lahbu.com.au/ In the footer, the email address is the button 

Add this code on custom css:
.secondary-button-style-outline .sqs-button-element--secondary:hover {

background: none !important;

}

Thank you, it works 🙂