how to remove white background?

[Alemantico]

Dear People,
at the very beginning it seemed to be a very easy task of styling VM, but I was very wrong! I.e. on my site https://dinnerdog.at/shop/canned-food.html, I tried to remove the white background (screenshot). By using firebug it pointed me to the button class. But even adding the property of "background-color: transparent !important" nothing changed. So I tried to take off all the bg properties in these files: component/com_virtuemart/assets/css/chosen.css, component/com_virtuemart/assets/css/vm-ltr-common.css  and component/com_virtuemart/assets/css/vm-ltr-site.css, but the damn ugly white background is still there! What on earth do I have to change, in order to get rid of that stupid white background? The mozilla-color picker is showing the code of "#d31b1b" or "rgb240,240,240". Most of them where applied inside the "chosen.css", but I'm still confronted with the problem!
Can please someone of you tell me about the magic trick?
Thank you very much in advance!

[AH]

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