Disable colors in emacs terminal

How to disable all colours in emacs _running in a terminal_? Note that I don't want disabling just a buffer. I don't want (global-font-lock-mode 0) because that only works on normal buffers, however emacs sometimes asks me questions in the mini-buffer in unreadable blue text, so I want to disable colours altogether. Alternatively a settings which just disables colours for the mini-buffer.