I was that guy to whom Kevin refers... we don't want to revive that debacle, I'm sure. By the way, appearance is only one of several things to consider when sleuthing a factory powder.
To the OP... I'm assuming you're interested in learning the powder HSM is using because their factory load is shooting well for you?
All well and good.
But here's what you do:
You have a good candidate or two for what the powder *might be*... emphasis on "might".
Compare same volume weights (use a Lee dipper, for instance, to see if equal volumes weigh the same)...
Burn a pinch in an ashtray, and see how they smell... and observe residue of burn.
The above two tests will rule out one or both of the suspected Hodgdon powders.
If equal volumes weigh the same... and burn test smells the same... then proceed---->
Go to Hodgdon - The Gun Powder People
and check out the load data they have for Retumbo or H1000.
Follow Hodgdon's (or other reputable load data, I think Hodgdon would be best in this case)...and you will begin working toward the charge you found in the HSM ammo KEEPING IN MIND NOT TO EXCEED THE POINT AT WHICH PRESSURE SIGNS OCCUR- (if any do). Do not exceed Hodgdon's maximum charge for the powder you're using.
Chronograph your loads also, and compare velocity to factory load. If you get to the same charge level (safely, following published load data and basic reloading safety practices)... and your MV is pretty much the same as the factory load... and accuracy is the same as well.... then you've probably sleuthed their powder.
I recently did the same basic thing to learn that Hornady is using 94 grains of Retumbo (Hodgdon's published max load) in their 285 grain 338LM match ammo. (this is in Hornady brass, by the way)...