Coloring agents and methods of use thereof

A functionalized dye comprising at least one chromophore and a color fastness moiety, wherein the chromophore is bound to the color fastness moiety by a linker, wherein said dye is a compound of formula Ia:

• C-L-F (Ia)
• wherein
• C is a chromophore selected from the following group:
• a diarylmethane chromophore, an azo chromophore, a nitro chromophore, a nitroso chromophore, or a substituted benzene chromophore;
• linker L is of formula (IIIa):
• wherein
• L covalently links C via the left hand side of formula IIIa to F via the right hand side of formula IIIa;
• a, b, c, d, and e are each 0;
• f is 1;
• R40, R41, R42, R43, R44, R45, R46, R47, R48, and R49 are absent;
• R50 and R51 are each hydrogen;
• E is NR52 or NR53C═O;
• R52 and R53 are each independently hydrogen or alkyl;
• F is a color fastness moiety represented by formula Va:
• wherein
• m is 0 or 1;
• n and o are 0;
• p, q and r are each independently 0 or 1, provided that at least one of m, p, q and r is not 0;
• R78, R79, R84, R85, R87, R88 and R89 are each hydrogen;
• R80, R81, R82, and R83 are absent;
• R86 is absent, hydrogen or hydroxyl;
• K is NR90, or C(═O)NR92;
• W is NR95R96, CR97R98R99 or OR100;
• R90 is hydrogen;
• R92 is hydrogen or alkyl;
• R95 is alkyl and R96 is hydrogen or alkyl, or R95 and R96, together with the nitrogen to which they are attached are linked to form a 4-8-membered heterocyclic ring comprising 1-3 heteroatoms;
• R97, R98 and R99 are hydrogen, hydroxyl, alkyl, alkoxy or heteroaryl;
• and
• R100 is hydrogen or alkyl;
• provided that the dye of formula Ia is not:
• or a cosmetically acceptable salt thereof.