When the list contains both horizontal and vertical splits, it is said to be organized in a two-dimensional split matrix where you can reference and access the Split properties using 2-D matrix notation. Here, the index of a split is the row number followed by the column number.

The following image shows the List control after setting the background color of a specific split.

The following code demonstrates how to access second vertical split (column) in the third horizontal split (row) and set its background color to light green.

this.c1List1.Splits[2, 1].Style.BackColor = System.Drawing.Color.LightGreen;