Started for myself some learning on colors in ConTeXt. In the manual there is a nice colorpalette shown (section 6, page 141). However, I cannot reproduce this. The following minimal example shows colored texts, but \showcolor[color-name] just produces black boxes with ominous zeroes behind it.
What am I missing here? The wiki didn't procure more information then the manual.

Hans van der Meer

\setuppapersize[A5][A5]
\switchtobodyfont[20pt]
\starttext
\color[red]{hello} \quad
\color[green]{hello} \quad
\color[cyan]{hello} \quad
\showcolor[red]
\showcolor[green]
\showcolor[cyan]
\stoptext