Die grauen Farben werden korrekt ermittelt.

src/Transformer/Utilities/HueSaturationValueToRedGreenBlue.php

@@ -49,6 +49,15 @@ class HueSaturationValueToRedGreenBlue
 
 
     protected function processConvert(): void
+    {
+        if ($this->saturation === 0.0) {
+            $this->red = $this->green = $this->blu = $this->value;
+        } else {
+            $this->splitColor();
+        }
+    }
+
+    protected function splitColor(): void
     {
 
     }