That retriever will become a valid destination for items it's set to receive (things you've placed in its inventory). If you've put nothing in the retriever's inventory, it will be a valid destination for all items. Whether or not it gets the color-marked items you intend it it to depends on how you've painted the tubes in between the sorting machine and retriever.
Really, though, the retriever is probably unnecessary. If you want the sorting machine to sort things into three different chests depending on the item type, you should do something like this:
1. Put three item types in sorting machine's slots, and color those three columns three different colors (say, red white and blue)
2. Connect tube from sorting machine's output to three different destinations (like chests)
3. Use a paint brush to color each of the three tubes connected to each chest red, white and blue. For instance, a red-tagged item will not travel down a blue-colored pipe, only a red or uncolored pipes.
4. Give the sorting machine some bluetricity
Basically let the sorting machine output into the tube network and let the color tags determine where things should go. I'm making some assumptions on what you're trying to do, however.
