[CLEANUP] Extract method Color::renderAsHex (#825)

An additional method to render in the "modern" syntax will soon be needed.
Splitting up the `render` method into sub-methods will help as a precursor to
that.

Author: JakeQZ

src/Value/Color.php

@@ -230,15 +230,9 @@ public function render(OutputFormat $outputFormat): string
             && $this->getRealName() === 'rgb'
             && $this->allComponentsAreNumbers()
         ) {
-            $result = \sprintf(
-                '%02x%02x%02x',
-                $this->aComponents['r']->getSize(),
-                $this->aComponents['g']->getSize(),
-                $this->aComponents['b']->getSize()
-            );
-            return '#' . (($result[0] == $result[1]) && ($result[2] == $result[3]) && ($result[4] == $result[5])
-                    ? "$result[0]$result[2]$result[4]" : $result);
+            return $this->renderAsHex();
         }
+
         return parent::render($outputFormat);
     }
 
@@ -266,4 +260,26 @@ private function allComponentsAreNumbers(): bool
 
         return true;
     }
+
+    /**
+     * Note that this method assumes the following:
+     * - The `aComponents` array has keys for `r`, `g` and `b`;
+     * - The values in the array are all instances of `Size`.
+     *
+     * Errors will be triggered or thrown if this is not the case.
+     *
+     * @return non-empty-string
+     */
+    private function renderAsHex(): string
+    {
+        $result = \sprintf(
+            '%02x%02x%02x',
+            $this->aComponents['r']->getSize(),
+            $this->aComponents['g']->getSize(),
+            $this->aComponents['b']->getSize()
+        );
+        $canUseShortVariant = ($result[0] == $result[1]) && ($result[2] == $result[3]) && ($result[4] == $result[5]);
+
+        return '#' . ($canUseShortVariant ? $result[0] . $result[2] . $result[4] : $result);
+    }
 }