Model Symbol Background Color

Hello Community,

I have come across a problem while modeling.

I've created a epc and there are some objects in it.

However the background of the text is white and I have no idea how to set the color to be transparent.

For example, the background color of the function below is white.

I've seen some examples in other models which is exactly what I want, which means that the background color is transparent.

Thanks in advance!