adding

src/scss/components/_panel.scss

@@ -7,38 +7,9 @@
 @mixin plain-ui__component__panel()
 {
     .panel {
-        border: 1px solid $plain-ui__primary-light;
-        border-radius: 2px;
-
-        background: #fff;
-
-        &__header {
-            display: flex;
-            background-color: $plain-ui__primary-light;
-            color: white;
-            padding: 0.8em 1.2em;
-            line-height: 1.6em;
-
-            button {
-                appearance: none;
-                background: none;
-                border: none;
-                padding: 0;
-
-                &:hover {
-                    cursor: pointer;
-                }
-            }
-
-            .icon {
-                vertical-align: bottom;
-                width: 1.5em;
-                height: 1.5em;
-                margin-right: 0.5em;
-
-                fill: white;
-            }
-        }
+        border: 1px solid var(--primary);
+        border-radius: $plain-ui__border-radius;
+        background: var(--white);
 
         &__buttons {
             display: flex;