Let's say I have a local

gen x=20
gen y=30
gen z=50

replace y = x+ y
replace z= x+y+z

loc x y z



twoway (area `x y z' date_ym , cmissing(no) sort), ///
legend(pos(6) rows(2)) ylabel(0(25)100)

As we can see, normally, the colour assigned to z would "dominate" the whole graph. I want each "smaller" portion of the area as a superseding layer of the graph (or assign a different color to areas with overlaps) Any clue how to do this?