The built-in themes

Theme	Appearance	Border	Density
dark	dark	single	normal
light	light	single	normal
console	dark	single	compact
paper	light	none	airy
workbench	dark	round	normal
mono	dark	ascii	normal

console, paper and workbench are the three house styles, and each is a handful of overrides on dark or light rather than a whole palette.

mono states monochrome: true, so it has no colour to give at all: every token resolves to the terminal’s own, and so does every literal a component carries. A banner or a chart drawn in its own colours is drawn in yours instead.