These photos of a German self-propelled howitzer in Afghanistan show its camouflage paint coating (the photos are several months old):
The camo looks appropriate in that region, doesn't it?
The only problem is that camouflage makes almost no sense for large vehicles over there. It's extremely unlikely that vehicles there will ever avoid being penetrated just because they used camouflage. It would take a lot of dust from vehicles driving ahead or a very partial exposure to allow the vehicle (crew) to avoid detection or to avert good aiming by the enemy.
The SPG will probably not even move much outside of the camp, for its range is about 40 km. It might leave the camp in support of more distant actions, but then it would most likely be stationary for most of the time and easily spotted and observed anyway simply because it's a huge tracked vehicle and not well-suited to running around much on a deployment that's going to last months or years.
I assert that this camouflage was applied without much thought - it was applied because it's what you do. Camo has become an end in itself for some.
I noted a similar phenomenon with Camouflage for choppers in Afghanistan a year ago.
What shall this howitzer do? It shall provide superior firepower and scare the enemy away (or kill him).
Imagine an impressive paint coating and a few life fire demonstrations - the whole province shall know the beasts. Give them a paint coating that means every child is going to remember them.
Don't give it a paint coating that looks as if you attempt to hide the SPG. Make it look fearsome, notorious, commanding respect. Tiger stripes maybe. Black-red-gold. Gold. Chrome. Paint a lion face on its glacis.
Whatever - just don't fall into mindless routine and give it a futile camo paint coating only because that's what's usually being done.
I am a huge fan of even extreme forms of camouflage (search for "camouflage" in the search box if in doubt), but camouflage is great because it's often an effective means to an end. There can be superior alternatives in some cases, and officers get paid to think about what shall be done. They should in my opinion arrive at the conclusion that this is such an exception.