\starttext

\defineprocesscolor[red][r=.5]

\blackrule[color=red,width=\hsize,height=1cm]

\defineprocesscolor[redish][red][a=1,t=.5]

\blackrule[color=redish,width=\hsize,height=1cm]

\defineprocesscolor[yellowish][red]

\blackrule[color=yellowish,width=\hsize,height=1cm]

\defineprocesscolor[yellowish][red][a=1,t=.5,y=.5]

\blackrule[color=yellowish,width=\hsize,height=1cm]

\defineprocesscolor[cyan][c=.5]

\defineprocesscolor[yellowish][cyan][y=.5]

\blackrule[color=yellowish,width=\hsize,height=1cm]

\stoptext
