To change the placeholder text color of a input element in HTML5, you can use the ::placeholder pseudo-element and the color property in CSS, like this:
input::placeholder {
color: red;
}
This will change the color of the placeholder text to red for all input elements on the page.
You can also use the ::placeholder pseudo-element to style other aspects of the placeholder text, such as the font size and font family:
input::placeholder {
color: red;
font-size: 20px;
font-family: sans-serif;
}
Keep in mind that the ::placeholder pseudo-element is not supported in all browsers. If you need to support older browsers, you can use a JavaScript solution to change the placeholder text color.