Careful now!

August 1st is a good day to pick the first blackberries but not everything that gleams blackly in the brambles is one.

My mother always used to say I went as brown as a berry in the summer. Thinking about this I started to wonder which berries are brown and could only come up with exotic ones such as allspice.
Apparently this "has long puzzled people" (!) but the putative explanations offered here are quite interesting.

More pertinently,  it seems that commercial berries are in short supply, and whole crops of fruit  and veg have been cooked brown by the recent scorching heat.
https://www.theguardian.com/environment/2022/aug/01/uk-farmers-count-cost-as-heatwave-kills-fruit-and-vegetable-crops