diplos look pretty much exactly the same exept for suttle differences only the trained eye can see, they are called the indian giant snakehead and were thought to be the same spiecies for a long time... they top out at 18 inchs to 2 foot in the aquaria so are sought after.
Having owned both (micros a number of times) I would say I have a trained eye.
Now not to say yours is for sure a Micropeltes, but from the pictures you have posted, it looks that way to me.
Diplos at that age/size USUALLY tend to have speckles of blue (sometimes black) around the body.
The body and especially the caudal fin also tend to have a vey blue hue to them too.
Micropeltes can vary in colors, pattern and shapes. The "flat grey top" theory is for sure not a way to ID a Micropeltes.
If you can post a clearer full body photo, can be more accurate for you.
Diplogramma, while not a common Channa, they are certainly not hard to find anymore, and prices are very reasonable now.
So if indeed yours does turn out to be a Micro, getting a Diplo shouldn't be too much trouble.