Just use the _selected modifier for wp-single-card

frontend/src/app/features/work-packages/components/wp-card-view/wp-single-card/wp-single-card.component.sass

@@ -146,7 +146,7 @@
     &_closed
       color: $spot-color-basic-gray-2
 
-    .op-wp-single-card_checked &
+    .op-wp-single-card_selected &
       background-color: $spot-color-main-light
 
   &--inline-buttons
@@ -157,7 +157,7 @@
     &.-show
       opacity: 1
 
-    .op-wp-single-card_checked &
+    .op-wp-single-card_selected &
       background-color: $spot-color-main-light
 
   &--inline-cancel-button