JSFiddle - React, Tailwind, and code Playground

HTML

<table cellspacing="0" cellpadding="3">
    <caption>
        Багана өнгө жишээ
    </caption>
    <colgroup>
        <col class="col1" />
        <col class="col2" />
        <col class="col3" />
        </colgroup>
    <tr>
        <th>Улаан</th>
        <th>Цэнхэр</th>
        <th>Ногоон</th>
    </tr>
    <tr>
        <td>1</td>
        <td>2</td>
        <td>3</td>
    </tr>
    <tr>
        <td>1</td>
        <td>2</td>
        <td>3</td>
    </tr>
    <tr>
        <td>1</td>
        <td>2</td>
        <td>3</td>
    </tr>
    <tr>
        <td>1</td>
        <td>2</td>
        <td>3</td>
    </tr>
</table>

CSS

table{border-collapse:collapse}
.col1 {background:blue}
.col2 {background:blue}
.col3 {background:green}
td,th{border:1px solid #000;padding:5px}