Yes. Blue is leeward
boat and rule 11 allows
her to luff if no other rule conflicts. Because Red and Blue have not yet reached
the two-length zone, they are, under normal conditions, not yet
"about to round" (however, see case
84, for discussion of "about to round" especially in heavy weather). Thus
rule 18 does not apply yet, and Blue is permitted to
luff if she complies with rule 16.