Shi / Hen for adjective + noun when discussing facts or perceived facts
@user970696 emmm i ve checked all your comments and i guess you are somehow mislead by some strict rules. You may have perceived that 很 more or less conveys comparison. 石炭纪的蕨类植物很大(The Carboniferous ferns are huge in size)(They are considerably huge compared with plants today)   这部电话很白 you more or less emphasize its white color. Why do you say that? The reason may come from the feature of generalized kind. (There are few phones that are so white)or from context (-我这电话买了十年了-那这电话很白啊)(-I bought the phone ten years ago-Oh, it's still that white!(It should looks old after using for so long)) So 我家猫很黑 is not simply "my cat is black". Try to learn different implication of 很:

我养的柴犬很黑(Because Shiba Inu is usually ginger)(So the comparison is between my dog and common Shiba Inu)
我的猫很黑，但毛却发亮(My cat is black, but he has shiny fur)(the comparison is between my cat and common black but dull cat)
蚂蚁很小(Ants are small compared with many animals we often see)

If you just say ...很... without explicit or inexplict comparison, it's correct but just strange.