Changing gridview row color on row command

Question

i have grid view with data say

1 xyz aaa  button
2 abc xxx  button
3 pqr ccc  button

what i want to do is on click of button (working On ROWCOMMAND) the row color should change.
i am able to change row color, ie when i click first row button its color changes to green, but when i click second row button then second row color changes to green but first row color also remain green.
i wan that only that row color should change whose button is clicked and rest should have its default color.
i want to do this in row command