\starttext

    \startluacode
        local function showtime(s,v,wd,ht)
            context.vbox()
            context.bgroup()
            context.offinterlineskip()
            for i=1,12 do
                context.hbox()
                context.bgroup()
                    for j=1,30 do
                        context.definecolor ( { "myhsv" }, { h = i * j, s = s, v = v } )
                        context.blackrule { color = "myhsv", width = wd, height = ht }
                    end
                context.egroup()
                context.par()
            end
            context.egroup()
        end

        for s=0.1,0.9,.1 do
            for v=0.3,0.7,.1 do
                showtime(s,v,"3mm","3mm")
                context.blank()
            end
        end

    \stopluacode

\stoptext
