Hi Annette,
To change the text link go to customizer > colors then change the Link & Accent Color.
And for hover effect in portfolio there isn’t any option to change the color from customizer. For this you need to paste the following code and change the hash value of color according to your choice, in child theme style.css.
#portfolio .post a:hover .overlay {
background: #3a3030;
}
If you don’t want to create child theme you can use this plugin. https://wordpress.org/plugins/wp-add-custom-css/
Thanks