how to change 1 div css on hover other div css code example

Example 1: hover on one div affect another

//cube is directly inside the container:
#container:hover > #cube { background-color: yellow; }

//cube is next to (after containers closing tag) the container:
#container:hover + #cube { background-color: yellow; }

//If the cube is somewhere inside the container:
#container:hover #cube { background-color: yellow; }

//If the cube is a sibling of the container:
#container:hover ~ #cube { background-color: yellow; }

Example 2: css hover change another element

#a:hover ~ #b {
    background: #ccc
}

<div id="a">Div A</div>
<div>random other elements</div>
<div>random other elements</div>
<div>random other elements</div>
<div id="b">Div B</div>