Got facebook policy warning for design of "login with facebook button" !

Hello Xtemos

I got a policy warning from facebook saying that the design of the “login with facebook” button is not as per facebook guidelines.

https://imgur.com/7plGoNH

After going back and forth many times on email as to what exactly is the issue I got the reply-

Hi,

Thank you for your reply. It seems as though the blue is not contrasted to the background blue so it is giving the impression that the white F is by itself and is not using the full blue box with white F in it. I would suggest changing to the white

box background.

Thanks,

https://imgur.com/ReopTXm

It seems strange that out of 1000s of users I have got this warning. However it seems I now would have to change the design of the button or stop using the same.

Can you let Me know how the same can be done? (Might not be a bad idea to change it in the theme only. If it is wrong for 1 site maybe other users will also get warning in future).