Dark Mode was released released with 6.7 Update 1 and of course it’s a much needed feature for VMware admins. This post shows the simple steps to change it for your vCenter in the vSphere Client and VAMI. I also show an issue it’s had since release and how to work around it.
vSphere Client
Click your username at the top right of the vSphere Client > Select Switch Theme

VAMI
When you’re logged in to the VAMI, Click the Actions Menu > Select Switch Theme

It’s good but it’s not perfect. I’ve noticed when editing text entries like Advanced Settings or Custom Attributes, the text is very dark so difficult to see when typing. It does change to white once you’ve finished but if you click in the field again, it goes back to a dark colour

If you want to check your typing, just select the text which makes it easier to read
