Grayed "Donate" Menu

[Kiss_The_Rain]

I found that when we click on any resources in Mayor house/Storehouse window, it will show a popup menu, one of them is "Donate x" where x is resource name we click. What is that ? And why it is grayed ?

Thank you very much for your assistance.

[SweaterPuppies]

There once was a event before my time where you donated resources to get balloons or something like that.