Show message if no notes match the filter;

src/views/Notes.vue

@@ -56,6 +56,15 @@
                             </div>
                         </div>
                     </template>
+                    <span v-if="colorToFilter !== '' && !notesExistInFilteredColor">
+                        Keine Notizen mit gewählter Farbe vorhanden<br>
+                        <a href="javascript:"
+                           class="color-change-button disable-filter-button"
+                           :style="'background-color: '+colorToFilter"
+                           v-on:click="colorToFilter = ''">
+                            Filter ausschalten
+                        </a>
+                    </span>
                 </div>
             </div>
         </div>
@@ -91,6 +100,15 @@ export default {
             note.color = color;
             this.$store.commit('saveNotes');
         }
+    },
+    computed: {
+        notesExistInFilteredColor() {
+            let component = this;
+
+            return this.$store.state.notes.filter((note) => {
+                return note.color === component.colorToFilter;
+            }).length;
+        }
     }
 }
 </script>