Panels are taken directly from Bootstrap, see the Panels docs for all that you can do with them.
All of default .panel’s are available .panel-primary, .panel-success, .panel-info, .panel-warning, .panel-danger but there are some custom Curated panel classes .panel--curated-1, .panel--curated-2, .panel--curated-3, .panel--curated-4, .panel--curated-5
Apply the modifier class .panel--curated-1 to any .panel to increase the border radius width.
Apply the modifier class .panel--curated-2 to any .panel to overwrite the .panel-heading background color.
Apply the modifier class .panel--curated-3 to any .panel to overwrite the .panel-heading background color and text color and pushes .panel-header in slightly.
Apply the modifier class .panel--curated-4 to any .panel to overwrite the padding.
Apply the modifier class .panel--curated-5 to any .panel to add background color to .panel-footer.