Struggling with button change.

Hi all, Ive been struggling figuring out how to make my buttons work correctly. For example clicking on first button sould change to black when selected but then when you click on the second button to select it, the first button should go back to default color vice a versa. But now you have to double click to deselect the one button. 

Example

https://xd.adobe.com/view/f4966677-3557-43ef-9f39-6bb5528549e4-a1c5/