I only tried with red maybe brown does it too idk

I'm having the same issue. Can't use shears on them either. Really bummed bc I want to be able to make the stuffed pumpkins :/

This was intended as parity with other crops, since you plant colonies from singular mushrooms. Its kind of an ambivalent choice, though; I can see why you'd want the colony itself here.

@shyrobot Chances are you're harvesting them too early. A full colony has 5 caps on its sprite, and must be mined with shears.

I understand why the not fully grown colonies would pick block to a singular mushrooms but the fully grown ones are a whole new block