default value for cascading dropdown is not working

[qtwqwc]

problem with default value cascading dropdown :Suppose parent dropdown is car (Values are car1, car2, car3)and its child is color(for car1 R Y G B, For car2 R Yand for car3 G B).Now on selection of car2 R and Y will appear and select R, then again made the change on car and select car3 then again select is comiing with G and B and select B.Now if I select again in car, car1 then the child is populating with the values of car1 but it takes the B as a default value as it was previously selected and also present for car1 too.This case is only happen. on select of child value which is availble for both parent selection