If you want a blue outline on an uiaxes, you could enter the following in the start up function:
set(app.UIFigure, 'WindowButtonMotionFcn', 'drawrectangle(app.UIAxes,''Position'',[0 0 1 1],''FaceSelectable'',false,''FaceAlpha'',0,''InteractionsAllowed'',''none'')');