Android Question checkbox square line color

I am moving my App to sdk26. I used in my App the default color (gray) for the checkbox square which was fine for my screen colors. Now in the sdk26 the default color seems to be the black color. I would like to get the option to modify it.
I looked in the checkbox attributes and tried using colordrawable variables but i did not find how to reach the square's line color parameter.
Could some body give me a clue ?
Thanks in advance