Was there any reason why many of these pieces are painted using blue?
Yes! Ceramics are fired in a kiln at high temperatures. Porcelain is fired at the highest heat (between 1,200 and 1,400 degrees celsius). There are few glaze colors that remain stable under such high heat. The metal cobalt that is used to create this beautiful blue is one of the few colors that can withstand the high temperatures in the kiln!
Thanks