Change color of post text and background

Hi All,

I want to change the color of my recent posts in the container so it displays white text on a black background (currenty it’s black text on a white background). I’m using layout-one. I tried the following css but it doesn’t work. Does anyone know where I’ve gone wrong?

.rt-tpg-container .rt-tag-layout1-buttons button {
color: #000000 !important;
}