I would like to change the color of an image with php. if I wanted to make it appear redder applicherei an image on a higher level across an image with a transparent red and
You can try using GD's imagecopymerge function, which copies one image to another and supports alpha transparency. Something like this should work:
<?php
$redimg = imagecreatetruecolor(100, 100);
$image = imagecreatefrompng('image.png');
// sets background to red
$red = imagecolorallocate($redimg, 255, 0, 0);
imagefill($redimg, 0, 0, $red);
// Merge the red image onto the PNG image
imagecopymerge($image, $redimg, 0, 0, 0, 0, 100, 100, 75);
header('Content-type: image/png');
imagepng($image);
imagedestroy($image);
imagedestroy($redimg);
?>
There's more information here.