How to change select background color?

You can change the select background color with CSS background. If it doesn’t work, add the !important at the end of the value (i.e. background: green!important).

Example:

<select style="background: #eee;">
    <option>Test option</option>
</select>

Output:

How to change the specific select option background color?

You can also style the specific select options, and append any background color to them.

Example:

<select>
    <option style="background: red;">Red</option>
    <option style="background: yellow;">Yellow</option>
</select>

Outut (toggle the list):