Hi Paul,
To change the font color of ‘Read More’ button text on homepage slider
Go to Appearance -> Theme Options -> Basic Settings -> Slider Caption Colors -> Select font color for slider button
To change the color of ‘Read More’ button text in Welcome section
Go to Appearance -> Theme options -> Basic Settings -> Custom CSS
and use below css code in custom css box and change color code as per your need
.view-all-btn a { color: #dd3333 }
Please check the documentation to customize the theme
https://www.gracethemes.com/documentation/zeroerror/
Regards
Grace Themes