Is it permissible to pay Zakat to a disabled colleague who took out a loan to get married? And is it permissible for colleagues to collect money for him as a gift?

It is permissible to pay Zakat to the one in debt (Gharim), because he is one of the categories of Zakat recipients. He is more deserving of it if he has special needs, as his disability may limit his ability to work. And collecting money for him as a gift from colleagues is a good deed for which one will be rewarded, based on the Prophet's (peace be upon him) saying: "Exchange gifts, and you will love each other," and his (peace be upon him) saying: "Allah helps the servant as long as the servant helps his brother."