Resolve "Terminkalender/Stundenplan: nur 15 Farben verfügbar"

Closes #3909

Merge request studip/studip!2765

resources/assets/stylesheets/less/schedule.less

@@ -265,6 +265,15 @@ td.schedule-adminbind {
         &.schedule-category15 {
             background-color: @calendar-category-15;
         }
+        &.schedule-category16 {
+            background-color: $calendar-category-16;
+        }
+        &.schedule-category17 {
+            background-color: $calendar-category-17;
+        }
+        &.schedule-category18 {
+            background-color: $calendar-category-18;
+        }
         &.schedule-category255 {
             background-color: @calendar-category-255;
         }
@@ -439,5 +448,38 @@ div.schedule_entry {
                 color: contrast(@calendar-category-15-aux, black, white);
             }
         }
+        &.schedule-category16 {
+            background-color: $calendar-category-16-aux;
+            border: 1px solid $calendar-category-16;
+            dt {
+                background-color: $calendar-category-16;
+                color: contrast($calendar-category-16, $black, $white);
+            }
+            dd {
+                color: contrast($calendar-category-16-aux, $black, $white);
+            }
+        }
+        &.schedule-category17 {
+            background-color: $calendar-category-17-aux;
+            border: 1px solid $calendar-category-17;
+            dt {
+                background-color: $calendar-category-17;
+                color: contrast($calendar-category-17, $black, $white);
+            }
+            dd {
+                color: contrast($calendar-category-17-aux, $black, $white);
+            }
+        }
+        &.schedule-category18 {
+            background-color: $calendar-category-18-aux;
+            border: 1px solid $calendar-category-18;
+            dt {
+                background-color: $calendar-category-18;
+                color: contrast($calendar-category-18, $black, $white);
+            }
+            dd {
+                color: contrast($calendar-category-18-aux, $black, $white);
+            }
+        }
     }
 }