Hi dusrkdldlr,
Which part of the design you want to change?
For example if you want to change change the background-color or border-radius on page identifier you can do it by accessing the classes of the elements you want to change :

.smart-pager .smart-pager-page-index-selector{
    border-radius: 0.25rem;
    background-color: rebeccapurple;
    color: white;

Or for a selected page identifier

.smart-pager .smart-pager-page-index-selector[selected]{
    background-color: blue;

Another option is to check this demo which shows the different pagination options:
Please, do not hesitate to contact us if you have any additional questions.
Best regards,
Yavor Dashev
Smart UI Team