How can PHP be used to create images with defined colors, and what functions should be used for this purpose?

To create images with defined colors in PHP, you can use the GD library functions. The functions `imagecreatetruecolor()`, `imagecolorallocate()`, and `imagesetpixel()` can be used to create an image with specific colors. First, create a true-color image with `imagecreatetruecolor()` function, allocate colors with `imagecolorallocate()` function, and then set pixels with specific colors using `imagesetpixel()`.

<?php
// Create a true-color image with dimensions 200x200
$image = imagecreatetruecolor(200, 200);

// Allocate a color (red in this case)
$red = imagecolorallocate($image, 255, 0, 0);

// Set a pixel at coordinates (100, 100) with the allocated color
imagesetpixel($image, 100, 100, $red);

// Output the image
header('Content-Type: image/png');
imagepng($image);

// Free up memory
imagedestroy($image);
?>