<div class="has">
    <div class="box">
        <p>spanタグがなければ背景が青</p>
    </div>
    <div class="box">
        <span><p>spanタグがあれば背景が赤</p></span>
    </div>
</div>
p {
  font-size:14px;
}
.has {
    margin-top: 40px;
    display: flex;
    gap: 8px;
    .box {
        height: 240px;
        width: 240px;
        background: #6495ed;//青
    }
    .box:has(> span) {
        background: #ed6464;//赤
    }
}

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