Hi
You need to apply the custom style code on the button css classes .
Copy class name : http://prntscr.com/bx3r2s
Check the style code used for templates button classes using inspect element : http://prntscr.com/bx3rnn
then apply the style on the jreviews button classes using custom.css file .
Example:
.jrButton
{color: #ffffff!important;
background-color: #ef553a!important;
border-color: #ed4122!important;
font-weight: 700!important;
padding: 10px 16px!important;
font-size: 11px!important;
line-height: 1.53846154!important;
border-radius: 3px!important;
background-image:none!important;
}