Hum, that should have been fixed since 2.4…
First, check that you use the last version of the plugin by going to “Edit/Plugins” and search for “Darker Nodes”
If you don’t, update it! If you do, go to “Edit/Editor Preference/Darker Nodes” and click on “Fix Missing Elements” (it’s normal that is does not check)
This should fix it! (but that’s weird since 2.4 should autofix this problem…)