Well, notes by original compilers of the IK have to be treated with some
caution. It has been a long while ...
However in the TROPICOS database the entry for P. coerulea includes
"Annotation: orth. variant for caerulea; caerulea is correct; use # 188"
which will be quite a bit better substantiated.

Anybody who can make out the spelling at the gallica site has better eyes
than I do, but caerulea is philologically preferable, caeruleus being Latin
for a shade of blue.
PvR

Iris Cohen schreef
According to the Missouri Botanical Garden database and Index Kewensis,
the correct spelling is P. caerulea. Apparently the name P. coerulea was
floating around at one time, but the compilers of the original Index
Kewensis put in a note: See P. caerulea.
Many things got a little messed up while crossing the English Channel. The
Mediterranean did a lot worse. Look what happened to the Hebrew alphabet
when the Phoenicians sent it over to Greece.
Iris,

=====
For the "blue" passiflora, the french write the epithet as COERULEA ,
the english CAERULEA, Both schools cite L. [1753, Sp. Pl. : 959],