\setupcolors [x11]

\definepalet [colorful] [primary=green]

\definepalet [bleak] [primary=darkgray,colorful]

\starttext
    \setuppalet [colorful]
    \color[primary]{Ain’t I a colorful entity?}
    \setuppalet [bleak]
    \color[primary]{Ain’t I a colorful entity?}
\stoptext
