Unable to style embedded iframe

Hi. I'm trying to style an embedded iframe and have been unable to do it.

Here is the website...

https://potato-chrysalis-h893.squarespace.com/

PW: Co$$ee

I'm trying to style the backgrounds of each event listing in the third section down, next to the Instagram embed.

This is where I last gave up...

div#block-yui_3_17_2_1_1732219200682_111359
.listing-event.event.category-adult {
        background-color:rgba(205, 238, 225,1);
        padding:0.25em 0.25em 0.25em 0.5em;
}

I've targeted classes in section IDs and block IDs and used different configurations of classes but nothing seems to work. When I inspect the code and try to adjust certain elements I am able to see the changes but only if I disengage certain other backgrounds or paddings first.

Ideas?

Hi, This cannot be done, because the content for the iframe is hosted on a different server. So the styling would have to be done in the hosts code. If I am understanding correctly.