I've read a grammar tip about 的 which I'm not sure I've completely understood (it's on page 7 here, if you can read Italian). It talks about using 的 to specify a quality.
An example is: 意大利的人 is different from 意大利人. In this case, I think the difference is between Italians as in "Italian people" (意大利人) and the people who live in Italy (意大利的人). This seems clear.
The other example, however，is about the difference between 白的马 and 白马, rendered respectively as "a horse whose color is white" and "a white horse". This seems to be a subtle difference and I'm not sure when I should use which. (Maybe it's just an arbitrary, "literary" choice?)
Then it goes on with a sentence example: to say "my horse is white" I'd use "my horse is a horse whose color is white" 我的马是白的(马). For an Italian native speaker, this is similar to the English idiom "he is a friend of mine" (in Italian you'd just say "è un mio amico", "he is my friend"): it sounds a bit off at first, but if that's how it works in Mandarin then that's what I will do. However, the point of my question is:
Would it be correct to use 我的马很白?
If it's correct, is there a semantic difference between 我的马很白 and 我的马是白的?