B6 doesn't have a true logo. The wordmark "jetBlue" is on all 5 tails in the picture with the 5th having the "new look" parallel bands of color on the tail.
The first 4 have the traditional tail designs which are something of a semi-logo since B6 is the only U.S. carrier to paint the tails like that even though no two are identical. Being a "domestic" carrier by airline standards - includes Caribbean/Mexico/Canada - B6 is the only carrier to paint the tails like that so the look is identifiable as being B6 although it's not a true logo.

Jim