累积定制的ggpairs（）将对象绘制到列表对象中

I am trying to create a list object that contains GGally plots. These plots are each created with two datasets, the main dataset and a subset of the main dataset to be plotted again in orange. In the MWE below, three plots are created, each comparing two columns from the mtcars data and each containing a different number of subset points to be plotted in orange:I am trying to create a list object that contai