We have 3 X Snom 320s in our office and 1 X Snom 370

Busy office with lots of incoming calls, if i pick up a call on my 370 and then need to transfer it, i can dial the internal extension of a colleague and press transfer button but then how can he tell which call is the internal call and which are the external calls coming in so he knows which one to pick up ?

Is there any setting for the phones to differentiate between external and transfers / internal calls on the led indicators or something ?