The colour difference is probably due to Australian/NZ cows almost always grazing pasture outdoors, whereas Japanese cattle are mostly housed. As well as the colour difference the Japanese refer to Australian milk as having an 'oceanic taint' - which is interesting since our milk probably tastes as milk should and milk from housed cattle should probably be referred to as 'lacking flavour'. Interestingly because of this taint issue the Japanese market prefers ice cream from producers in northern Australia since our cattle have a relatively higher grain component in their diet which reduces the 'taint' somewhat.
Good to hear your cheesemaking went well. There are a couple of small scale cheesemaking dairies in Japan. I noted down their location for safe keeping somewhere. When I remember where it is I'll let you know. NV.