I'm pretty sure it's older canon that briefings are hypnotherapy, yes. Still, my point was that once you're deployed and possibly cut off from all chapter support for months of time if you're working in less than ideal conditions (not every Space Marine deployment is a lightning strike against command elements to remove the head of the snake, followed by a perfectly-executed evac by Thunderhawk. Sometimes, they're required to hunt their target because there are no Assassins available in the sector and they can't afford to wait; sometimes, they need to strike without the possibility of support because time is of the essence), it's not possible to "top-up" the hypnotherapy.
The tragedy of 40k's grimdark is that the CSM are really the good guys, at least in their original intentions, but they've been corrupted by their humanity and if they win, the universe will destroy itself in the grip of the Ruinous Powers.
> I think that's going too far towards making them generic power armored soldiers, but something of a balance would be nice.
Camo is pretty damn useful, and it's in the Codex Astartes. The entire "do not defile the colours of our chapter" angle came after GW reimagined SM as space-monk-knights with FIGHTAN HONOR.
The whole point of the Codex Astartes and SM is that they will use whatever tactic is most appropriate to the situation. If the situation requires them to repaint their armour in camo patterns to minimise casualties, they will do that. If the situation requires them to wear garish colours and shout war-cries at the top of their lungs to scare the living daylights out of the enemy, they will also do that.