Just what i want
This is the editor

There is a bug for the individual rounded corners in buttons but you can use a label instead.
See a workaround for rounded buttons.
I made the button transparent and rounded the row containing the buttons and made the row background color the color of the button.
https://x.thunkable.com/projectPage/6169340e438c7400103b75ad
But I want one color on the left and one color on the right.
If all what you want to do is the user click on them then use Labels
because they will give the same effect and works with rounding one side only.
Really? 2M ago, I found that the label cannot be rounded.
Really
Label works fine
You can remix the same project and see it in action.