I think this scenario illustrates a point that is perhaps not as well understood as it should be.  The four primary rules (i.e. Port/Starboard, Windward/Leeward, Ahead/Astern & Keep clear while tacking), never go away or 'turn off'.  The subsequent rules limit what the right of way boat can but do not remove the responsibility of the keep clear boat to keep clear.  In this case, once green is established on starboard, red is windward boat and must keep clear under Rule 11 (and Rule 14).  If red believes that she had to luff above close hauled, then her redress is to protest.  If she makes no attempt to keep clear and contacts green then she has broken both rule 11 and rule 14.  If there is a collision, red will be at fault unless she can demonstrate that green did not give her room to keep clear, regardless of whether green broke rule 18.3.

A similar situation occurs when overtaking to leeward.  Once an overlap is established the windward boat must keep clear (although she must be given room to keep clear).  If she believes the leeward boat is sailing above her proper course (and that is not necessarily straight for the mark) then she can hail and/or protest, but she cannot just ignore the boat overtaking to leeward and sail whatever course she likes.

I would like to qualify John949's second paragraph above.

When the leeward overlap occurs in the zone and 18.3 applies, (Red enters the zone on stbd, and Green tacks to stbd in the zone, and Red gains an inside overlap), then Red gains mark room (second part of 18.3).

The significance of this is that Red, while sailing within what mark room allows, shall be exonerated under R43.1(b) if she breaks R 15 or R 16.1 or R 31.

John

John

The second para wasn't to do with rounding marks per se.  It was just a gripe that many people seem to think the old 'overtaking boat keep clear' rule still exists and squeeze down on you when the should actually be keeping clear.  The rules limit the overtaking boat to sailing it's proper course but the windward boat still has to keep clear.