It depends on which version of the SPLITTY4 you have. One version (not sure if it is the new or the old) has RGB ports labeled 'in' and 'out.'
Lol, wasn't aware of the upgrade. It should have been named splitt4+, or something to distinguish it from the old version... like the splitty9 active.
If one researches the item at aquacomputer's shop, but purchases at ANY other vendor, one may not get what one expects.
All the vendors I checked still have the old version... a bit devious.