What will happend if a request in Green is deleted?

Deleting green request is no harm. if you are loading via psa, you can go to tab 'reconstruction' and select the request and 'insert/reconstruct' to have them back.But,
For example you will need to repeat this delta load from the source system. If you delete the green request then you will not get these delta records from the source system.

Explanation :
when the request is green, the source system gets the message that the data sent was loaded successfully, so the next time the load (delta) is triggered, new records are sent.
If for some reason you need to repeat the same delta load from the source, then making the request red sends the message that the load was not successful, so do not discard these delta records.Delta queue in r/3 will keep until the next upload successfully performed in bw. The same records are then extracted into BW in the next requested delta load.