diff --git a/lib/Validators/LabelServiceValidator.php b/lib/Validators/LabelServiceValidator.php
index 7ccbb57d2..720994bce 100644
--- a/lib/Validators/LabelServiceValidator.php
+++ b/lib/Validators/LabelServiceValidator.php
@@ -10,12 +10,16 @@
 namespace OCA\Deck\Validators;
 
 class LabelServiceValidator extends BaseValidator {
+	protected function hex_color(string $value): bool {
+		return preg_match('/[A-Fa-f0-9]{6}/', $value) === 1;
+	}
+
 	public function rules() {
 		return [
 			'id' => ['numeric'],
 			'title' => ['not_empty', 'not_null', 'not_false', 'max:100'],
 			'boardId' => ['numeric', 'not_null'],
-			'color' => ['not_empty', 'not_null', 'not_false', 'max:6']
+			'color' => ['not_empty', 'not_null', 'not_false', 'max:6', 'hex_color']
 		];
 	}
 }
diff --git a/src/mixins/color.js b/src/mixins/color.js
index e3bf94bb3..88ee62d35 100644
--- a/src/mixins/color.js
+++ b/src/mixins/color.js
@@ -3,11 +3,15 @@
  * SPDX-License-Identifier: AGPL-3.0-or-later
  */
 
+import { isDarkTheme } from '@nextcloud/vue'
 import chroma from 'chroma-js'
 
 export default {
 	methods: {
 		textColor(hex) {
+			if (!this.colorIsValid(hex)) {
+				return isDarkTheme ? '#ffffff' : '#000000'
+			}
 			return chroma(hex ?? 'ffffff').get('lab.l') > 50 ? '#000000' : '#ffffff'
 		},
 		colorIsValid(hex) {