CTA Customization - Transparent Background, Different Hover Colors


I need to create a CTA button that mimics the exact colors/hover colors the Request Demo button on this website’s home page: https://www.5nine.com.

While I was able to customize the button well enough to get the transparent background with white border and have the white background on hover, I have not been successful changing the color of the text on hover in the custom CSS tab of the CTA.

Can anyone help me so I can customize the colors for hover? I have no idea what CSS file these CTAs pull from if any to add a custom class. I spoke to support and they had no idea how to do this. Can someone please help? My boss wants me to replace all buttons and links on the website by EOD tomorrow with Hubspot CTAs.

Thanks for any help!