Hello @ArtOfSpring,
Thanks for updating the thread. 
I inspected the page and can see that in sidebar widgets there’s a text shadow effect and because of that you see variance in the display of button.
In Order to remove text shadow from sidebar widget thus making button in sidebar look like similar to left side content area buttons. To do that please add following CSS under Pro > Theme Options > CSS:
.widget {
text-shadow: none !important;
}
1- I have found the proper CSS code selector using the Chrome browser Developer Toolbar: https://www.youtube.com/watch?v=wcFnnxfA70g
2- For the CSS code itself, I suggest that you get started with this tutorial: https://www.youtube.com/watch?v=yfoY53QXEnI
Thanks.