Ben captcha resim türü senaryo üzerinde çalışıyorum ve benim görüntü üzerindeki her harf renk alternatif isteyen am, şimdiye kadar beklediğim renk değerleri dışında hemen hemen değil çalışma var

The colors in this $multi_text_color variable should be the colors that it randomly picks and shows, it does work in randomly picking the color array value however the colors it is putting on the image are 3 colors no where near to what I want, so am I doing something wrong here?

<?PHP
// note this is just the part I am having trouble with, I have taken everything else out that adds line and tilts the letters and stuff so just the color settings are in this bit

// My this part of my script takes each number/letter in a string and makes it a random color to put on the image

// set color values
$multi_text_color = "#FF3E96,#6A5ACD,#90EE90";
// put colors above into an array
$colors = explode(',', $multi_text_color);
// cycle through everything to add the letters/numbers to image
for($i = 0; $i < $characters; ++$i) {
    $idx = rand(0, 2);
    // notice my $colors variable has random number for the color array
    $r = substr($colors[$idx], 1, 2); // shows: f6 or 8d or FF
    $g = substr($colors[$idx], 3, 2); // shows: 3E or 32 or 5c
    $b = substr($colors[$idx], 5, 2); // shows: 96 or 47 or fd 
    $font_color = imagecolorallocate($image, "$r", "$g", "$b");
    // finish it up
    imagettftext($image, $font_size, $angle, $x, $y, $font_color, $this->font, $code{$i});
}
?>