So I was playing as my apoth. I had a chainsword and thus an adrenaline vial. I spent nearly half a minute trying to chase around a ground assault who was running into combat with my syringe so I could buff him .When I finally did he asked why I didn't do it sooner. I told him I'd been following him and he said he thought I had been trying to give him HoT. Which brings me to my point: You can't tell what vial an apothecary has equipped.

My proposed Solution is to make a visual cue by which other players can Identify your Vial type. The Apothecary bears a backpack as do all marines. On the right side of that backpack there is a small red cylinder. My suggestion is have that cylinder change colors depending on the vial.

see the red colour tube thing of the backpack, change its colour to ID which vial the apoths carrying..that simple

That's the idea, yes. Unless that was sarcasm. Then my answer is I don't know how hard it is to do that, but way back before early access I commented on the apothecary backpack light not being on and they updated that to be on in an afternoon by changing its color. So it seems easy enough?

Not sarcasm. Just stating what should be a future no brainer for IDing the vial type. Glad u brought it up as i thought about that question to.