Besides the classes used for messages (code, comment, var, warning, error, truth(Truth), port(Port), message(Kind), ...), the interactive toplevel uses these:

prompt

The ?- prompt and its ‘| ‘ continuation.

input

The text typed by the user at the prompt.

answer(Parity)

An answer written by the toplevel. Parity is odd or even and alternates over the answers of a single query, which allows for striping the answers using a background color. Only an answer that shows bindings, residual goals or delays uses this class: true. and false. are not answers to stripe, and neither is the empty line that separates the answer from the next query.

binding(name)

The variable name in a binding such as X = 1.

The debugger uses, besides frame(level) and port(Port):

goal(Port, Parity)

The goal of a frame reported for Port. Parity is odd or even and alternates over the steps of a trace, which allows for striping the goals using a background color. Match on Port to color the goal by port instead of (or in addition to) striping.

Note that a background color on prompt, input or answer(_) is painted up to the right margin using ‘\e[K`. A background on goal(_,_) is not: the debugger writes its ? prompt on the same line.

See also

library(theme/dark) for an example implementation and the Term values used by the system messages.