How to check HTC desire is off without turning it on? Is is possible somehow to distinguish between the phone being off or sleeping without turning it on in the process (this happens when pressing the power button)?

I appreciate that I can just use silent or airplane mode rather than turning it off, but was  interested to see if there was a way.
This is for the HTC 1.  You'll have to see if it works for you.  The charge light is red when the phone is off, and orange when it's on.  Obviously, that's with the charger connected.