Vaadin 8 - Calendar add-on adding background color doesn't take effect

I’ve using [calendar add-on]
(http:// for vaadin 8 (as we don’t have calandar component in vaadin 8). The problem is even though adding background color style in scss file, background doesn’t change. Actually as I see in chrome-dev tools style gets added to different div class instead of intended class and override calendar component style. Please help in this issue, for reference please find attached image.