So i am trying to customize a full dropbox (Country Selector) instead of the regular look, I want to add a diferent design to it.

Regular design

[

The Design I want

The first image is the default version with color adjustments, its the version that is working on the website, I want to make the design look like the 2nd picture i've uploaded.

The second version is what I got on photoshop, how i do customize my <select> to the 2nd picture? here is the code i got on css, I tried to use ::webkit and it didn't work.

CSS

.paistofill option {
    background-color:#a5e4c9;
    font-weight: normal;
    white-space: pre;
    min-height: 0.0em;
    padding: 0px 0px 0px;
    border-radius: 50px;
}

.paistofill select{
    background-color: white;
    color:#a5e4c9;
    border-radius: 50px;
}

The select customization has no effect on the element, what do I need to do?