The Sort-O-Tron is (as the name indicates) a sorting machine. In the GUI, you can define what items to sort.
The GUI + Usage
In the bottom of the GUI is a row of paintbrushes, you can click them to change colour. Each paintbrush corresponds with column of inventory slots above it. Any item that passes through will be matched with the items programmed into the slots. If the item matches it will colour the passing item the colour of the paintbrush of the column the item is in.
The most left paintbrush doesn't have a column of slots to program. Items that don't match anything programmed in will be painted that colour.