The Colour of Paraguayan Uniforms?

So the Osprey has come through in the post and I have embarked on more serious reading regarding the Chaco War. But after a basic flick through I've got a conundrum...
The Paraguayan Infantry I have already painted were colour wise based on this image:

It's the front cover of the Osprey as I found it on google images, the Paraguayan Infantryman being the man in the centre (if you hadn't already guessed). One thing the Osprey has inside is lots of actual photographs of soldier during the war and a number of images of Paraguayan Infantry. One such image (not in the Osprey but which emphasises my point) is:

Now I'm not sure if it's a trick of the light or camera, or if there is a point in the Osprey I haven't yet gotten to, but the majority of the images I can find of Paraguayans would lead me to believe that their uniforms are infact, at least in the majority far lighter than the cover of the Osprey would lead you to believe. One of the few images I found to the contrary was this one:

But I would still say the uniforms are a few shades lighter than the Osprey, and there's a fair few lighter shirts and trousers dotted around. So maybe it's closer to the truth to paint my troops in a much lighter yellow-green as opposed to the olive (castellan green) I was using.

Just a thought, thanks for stopping by!

WGP