Customize gradient buttons

Hi, Thanks for a great theme. I've been wanting to customize the gradient colors of the buttons, say on the front page. I've been trying to change the colors in the theme editor, but that doesn't seem to effect it strangely. Am I missing something? I also tried to enter this code into the Custom CSS editor, and allthough it changes while in the editor, the changes doesn't become permanent on the site. a.readmore.customize-unpreviewable { background-image: linear-gradient(to bottom, #28285b, #c0ded3) !important;