imagecolorallocate(): Red component is out of range getting error while getting captcha image

Question

I have a issue with PHP 7.4.5. I have an CaptchaExtendedAction Extension in Yii1 and sometime I get this error:

imagecolorallocate(): Red component is out of range

at this line

$foreColor = imagecolorallocate($image, mt_rand($r-50,$r+50), mt_rand($g-50,$g+50),mt_rand($b-50,$b+50));

Anybody has an idea how to avoid this?