Picking up briefly on the connection between blackberries and the colour black - blackberries, mulberries and blackcurrants are so very dark red they appear black when ripe, and leave a dark purple stain on skin and clothes. Mulberries grow on trees (blackberries are the fruit of the bramble briar, which is a hedgerow plant, and blackcurrants grow on a bush). The phrase about the blackberries being less good after the Devil has touched them is to do with the likelihood of frost damage rather than their colour. You wouldn't want to eat an unripe (red or green) blackberry so there's no negative association with the colour itself.

It might be interesting in this discussion of the word "black" to say that black as the colour of mourning in most of Europe was a very late development (possibly as late as Victorian times)as black was a very expensive dye for clothing until that time. Someone dressed in black was perceived as high status and wealthy - in the case of the Devil he was dressed in a most distinctive colour.

As to black animals, black skins etc being perceived as evil - in a society where the norm was a white skin (or a pink pig, or a white sheep) it's surely just a departure from what was considered normal, rather than anything else?   Just as someone with an extra finger was looked at with suspicion, and any kind of mental illness was treated as possession by the devil.