Add custom exception MDInvalidColorCode

exceptions/generic/MDInvalidColorCode.php

@@ -0,0 +1,19 @@
+<?PHP
+declare(strict_types = 1);
+
+/**
+ * Exception thrown in case a color code is not valid.
+ */
+final class MDInvalidColorCode extends MDgenericInvalidInputsException {
+    /**
+     * Error message.
+     *
+     * @return string
+     */
+    public function errorMessage() {
+        //error message
+        $errorMsg = 'Input color code is invalid';
+        return $errorMsg;
+
+    }
+}