JSFiddle - React, Tailwind, and code Playground

HTML

<table>
		<caption>Таблица 1</caption>
		<colgroup>
			<col>
			<col>
		</colgroup>
		<colgroup>
			<col>
		</colgroup>
		
			<tr>
				<td>1</td>
				<td>1</td>
				<td>1</td>
			</tr>
			<tr>
				<td>2</td>
				<td>2</td>
				<td>2</td>
			</tr>

	</table>
  
  <table>
		<colgroup>
			<col>
			<col>
		</colgroup>
		<colgroup>
			<col>
		</colgroup>
		
			<tr>
				<td>1</td>
				<td>1</td>
				<td>1</td>
			</tr>
			<tr>
				<td>2</td>
				<td>2</td>
				<td>2</td>
			</tr>

	</table>

CSS

colgroup:first-child {
  background-color: yellow;
}

colgroup:nth-child(2) {
  background-color: red;
}