nikofedorov,
если чуть чуть влезть
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
.shop_spec_val {
background-color: var(--bg, transparent)
}
</style>
<script>
document.addEventListener("DOMContentLoaded", _ =>
document.querySelectorAll(".shop_spec_val")
.forEach(({style: s, textContent: t}) => (t = Number(t),s.setProperty("--bg",
t >= 90 ? "Green": t >= 75 ? "Yellow": t >= 50 ? "Red": "Gray")))
);
</script>
</head>
<body>
<table width="400" summary="" >
<thead>
<tr>
<th>Title 1</th>
<th>Title 2</th>
<th>Title 3</th>
<th>Title 4</th>
</tr>
</thead>
<tbody>
<tr>
<td class="shop_spec_val">90</td>
<td class="shop_spec_val">30</td>
<td class="shop_spec_val">70</td>
<td class="shop_spec_val">80</td>
</tr>
<tr>
<td class="shop_spec_val">90</td>
<td class="shop_spec_val">30</td>
<td class="shop_spec_val">70</td>
<td class="shop_spec_val">80</td>
</tr>
</tbody>
</table>
</body>
</html>