The Pigment Blue 78 with the CAS number 68921-42-6 is also called C.I. Food Blue 2 aluminum lake.The systematic name is Benzenemethanaminium, N-ethyl-N-(4-((4-(ethyl((3-sulfophenyl)methyl)amino)phenyl)(2-sulfophenyl)methylene)-2,5-cyclohexadien-1-ylidene)-3-sulfo-, hydroxide, inner salt, aluminum salt. Its EINECS registry number is 272-939-6. The molecular formula is C₃₇H₃₆N₂O₉S₃^.xAl.

Properties Computed from Structure: (1)XLogP3-AA: 4.7; (2)H-Bond Donor: 2; (3)H-Bond Acceptor: 10; (4)Rotatable Bond Count: 11; (5)Exact Mass: 748.158293; (6)MonoIsotopic Mass: 748.158293; (7)Topological Polar Surface Area: 197; (8)Heavy Atom Count: 51; (9)Formal Charge: 0; (10)Complexity: 1630; (11)Isotope Atom Count: 0; (12)Defined Atom StereoCenter Count: 0; (13)Undefined Atom StereoCenter Count: 0; (14)Defined Bond StereoCenter Count: 0; (15)Undefined Bond StereoCenter Count: 0; (16)Covalently-Bonded Unit Count: 1.

You can still convert the following datas into molecular structure:
(1)SMILES: c1(ccccc1/C(=C/1C=C/C(=[N+](\CC)Cc2cc(ccc2)S(=O)(=O)[O-])C=C1)c1ccc(cc1)N(CC)Cc1cc(ccc1)S(=O)(=O)O)S(=O)(=O)O
(2)InChI: InChI=1S/C37H36N2O9S3/c1-3-38(25-27-9-7-11-33(23-27)49(40,41)42)31-19-15-29(16-20-31)37(35-13-5-6-14-36(35)51(46,47)48)30-17-21-32(22-18-30)39(4-2)26-28-10-8-12-34(24-28)50(43,44)45/h5-24H,3-4,25-26H2,1-2H3,(H2-,40,41,42,43,44,45,46,47,48)