[test] add DOM property assertions for Vue node colors - addresses review feedback

Adds CSS background-color property validation in addition to screenshot comparison
to verify header and body colors are correctly applied to DOM elements.

Co-authored-by: Myestery <Myestery@users.noreply.github.com>

browser_tests/tests/vueNodes/nodeStates/colors.spec.ts

@@ -28,6 +28,18 @@ test.describe('Vue Node Custom Colors', () => {
     await expect(comfyPage.canvas).toHaveScreenshot(
       'vue-node-custom-color-blue.png'
     )
+
+    // Verify actual DOM properties for header and body colors
+    const nodeHeader = loadCheckpointNode.locator(
+      '[data-testid^="node-header-"]'
+    )
+    const nodeBody = loadCheckpointNode
+
+    // Header should have blue header color (#223)
+    await expect(nodeHeader).toHaveCSS('background-color', 'rgb(34, 34, 51)')
+
+    // Node body should have blue body color (#335)
+    await expect(nodeBody).toHaveCSS('background-color', 'rgb(51, 51, 85)')
   })
 
   // TODO: implement loading node colors from workflow in Vue system