Whenever you changed the theme color, you will noticed that the button text color in the View and Buy Now buttons becomes unreadable.
To fix the button text, please edit css of your chosen theme color. If you choose blue, then edit blue.css via FTP or Notepad++. If you choose Turquoise as theme color, then edit turquoise.css.
Go to wp-content > themes > instaportfoliopro > css > blue.css > delete !important in line 5
Code should look like this:
a {color: #f55d0a;text-decoration: none;}
a:visited {
color: #ffcaad;
Make sure to update the file to save the changes.
Note: Always make a backup file before changing anything in the code.