to answer myself, view color changes via canvas so it is
v canvas color: Color black.��
I also found a way to create an edge looking at the tests.��
this is the complete code now
v := RTView new.
shape := RTEllipse new size: 20; color: Color red. shape := shape + RTLabel.
es := shape elementOn:'hello'. v add: es.
el1 := RTBox element.
el2 := RTBox element.
el1 translateTo: 20 @ 20.
el2 translateTo: 60 @ 80.
edge := RTLine edgeFrom: el1 to: el2.
"es2 := edge element."v add: edge.
"RTEdge buildEdgesFromObjects: (1 to: 20) from: [ :i | i // 2 ] to: #yourself inView: v". "RTGridLayout on: es".
es @ RTDraggable.
v @ RTDraggableView .
v canvas color: Color black.
v open.
probably there is an easier way to do this so I am taking a look at both tests and examples.