JSFiddle - React, Tailwind, and code Playground

HTML

<div class="indicator">Style</div>
<div class="mainPanel">
    <div>T</div>
    <div></div>
    <div>Speichern</div>
</div>

CSS

.indicator {
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
    position: absolute;
    width: 300px;
    text-align: center;
    z-index: 10;
}
.mainPanel {
    width: 300px;
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
    display: flex;
}
.mainPanel > div {
    text-align: center;
    padding: 0 10px;
    white-space: nowrap;
    border: solid 1px #999;
    
}
.mainPanel > div:nth-child(1) {
    background: red;
}

.mainPanel > div:nth-child(3) {
    background: lime;
}

.mainPanel > div:nth-child(2) {
    background: yellow;
    flex-grow: 1;
}