What potential pitfalls should be considered when modifying PHP code for color differentiation in output?

When modifying PHP code for color differentiation in output, potential pitfalls to consider include ensuring compatibility with different browsers, maintaining accessibility for users with visual impairments, and avoiding hardcoding colors that may clash with existing styles or themes. It is important to use CSS classes or inline styles to apply colors, rather than directly manipulating HTML elements with PHP code.

echo '<div style="color: blue;">Blue text</div>';
echo '<div style="color: red;">Red text</div>';