Both. Safety requires Red to make a substantial course change to avoid Green
that ranks as obstruction. Therefore Red is entitled by rule 20.1 to hail for room
to tack. Blue has to respond as required by rule 20.2(c). Because Blue
fails to respond she shall be penalized for breaking rule 20.2(c). When it became
clear that Blue was not giving room by tacking Red has the possibility to keep
clear by passing astern of Green. In failing to do this, she shall be penalized
for breaking rule 10.