Okay, kiddo, so you know how we have different colors for different things, like red for stop signs and green for go signs? Well, a long time ago, there was a man named Saint Patrick who was really important in Ireland. And in Ireland, they had a color that they used for important things like princes and kings. That color was called Saint Patrick's Blue.
Nowadays, people usually use the color green for Saint Patrick's Day, which is when we celebrate Saint Patrick. But some people still like the color blue because it reminds them of the history and tradition of Ireland. So it's like a special color that people remember from a long time ago.