Hi Drew,
Thank you for reaching out!
Please be aware that to reduce repetition in CSS, and improve powerful runtime effects like theme switching, we use variables to customize our theme. A specific color set in the customizer might be used in multiple place.
To change the color when hovering the user name, please go to Customize > Posts > Posts Page > Item. Then, please change the Link Color Hover. Note that this color is also used when hovering the topics.
To change the color of the text on the top of the page, please change the Text Color in the same place.
Please find the attached screenshot.
Kind regards,