Space between h3 and body

I need to tighten up the space between the h3 and the body text on the landing page only.

I have tried
#top .all_colors p {
line-height: 1.5em;
margin: 1em 0;
}

Dropped the margin to .1em 0;
works fine in google’s inspector, but enteing it as a .css rule it has no effect.

I tried isolating it from the rest of the site by using

/* try to remove margins on p on one page */
#top .page-id-4022 .all_colors p {
margin-top: .1em;
margin-right: 0px;
margin-bottom: .1em;
margin-left: 0px;
}

No love