What are the different kinds of shrines and how do they work?

I've encountered an "Ammo Shrine" while playing through the 'Tiny Tina's Assault on Dragon Keep' DLC:

How does it work? Also, are there other types of shrines in TTAoDK? If yes, what does each type of shrine do?

It seems that at least two shrine effects can be had at the same time. How will this stack (if for example I have two shrine effects from the same shrine type active)? Up to how many shrine effects can I stack?

Also, there seems be a cooldown before you can re-activate a shrine - how long is this?

Green gives you very fast ammo regen.

Yellow gives you large amounts of speed.

Blue Defense gives shield regeneration.

Red Defense gives health regen.

Melee gives massive knockback to all of your melee attacks and increases melee damage.

Damage simply makes you do more damage.

There are Defense, Melee and Ammo shrines, and possibly others I haven't seen. Only one player can activate them at a time, but they reactivate and allow you you buy the buff again after a few while (possibly after the first buff ends?). So don't be afraid of "wasting" them, though note that if you grab a buff your friends will either have to wait or pass on that buff.

They are found in set locations, often at key points (boss battles, areas with lots of enemies) on maps.

• Ammo:

  • Color: green
  • Cost: E2
  • Effect: For several seconds, ammo for the currently equipped weapon (not grenades, unsure about rockets) will regenerate extremely fast. Not useful for "infinite ammo" but rather a quick way to completely refill a couple ammo types, even mid-combat. Even with SMGs you will replenish at least as much ammo as you shoot, and you will regain at least 50% or more of your ammo before the effect finishes.

• Defense

  • Color: Blue
  • Cost E2
  • Effect: Unsure, haven't used this yet
• Melee
  • Color: purple?
  • Cost E2
  • Effect: Unsure, haven't used this yet
• Damage
  • Color: Orange
  • cost: E2
  • Effect: Unsure, havn't used this yet
• Speed
  • Color: Yellow
  • Cost: E2
  • Effect: You move very quickly for the duration of the shrine.