A composition, including a mixture of: a compound of Formula wherein A is a C 2-8 alkylene group; R 1 is selected from hydrogen, C 1-4 alkyl, and C 2-4 dihydroxyalkyl in which the carbon atom attached to the nitrogen atom does not carry a hydroxyl group and no carbon atom is substituted by two hydroxyl groups; R2, R 3, and R 4 are independently selected from C 1-4 alkyl, C 2-4 dihydroxyalkyl in which the carbon atom attached to the nitrogen atom does not carry a hydroxyl group and no carbon atom is substituted by two hydroxyl groups, or R 2 and R 3 together form a C 2-6 alkylene group which with the nitrogen atom to which R 2 and R 3 are attached forms a heterocyclic ring; X 1, X 2, and X 3 are independently selected from hydrogen, hydroxyl, NR 1 -A-NR 2 R 3 R 4 +(Z m-) 1/m, halogeno amino, C 1-4 alkoxy or C 2-8 alkanoyloxy; and (Z m-1) 1/m is an anion of charge m; or a derivative in which the group NR 1 is quatemarized together with at least a second fluorochrome or light-emitting compound, wherein the compound is of Formula or an N-oxide derivative thereof; wherein A is a C 2-8 alkylene group; R 1, R 2, and R 3 are independently selected from hydrogen, C 1-4 alkyl, C 2-4 dihydroxyalkyl in which the carbon atom attached to the nitrogen atom does not carry a hydroxyl group and no carbon atom is substituted by two hydroxyl groups, or R 2 and R 3 together form a C 2-6 alkylene group which with the nitrogen atom to which R 2 and R 3 are attached forms a heterocyclic ring; and X 1, X 2, and X 3 are independently selected from hydrogen, hydroxyl, NR 1 -A-NR 2 R 3, halogeno amino, C 1-4 alkoxy or C 2-8 alkanoyloxy. a compound of Formula wherein A is a C 2-8 alkylene group; R 1 is selected from hydrogen, C 1-4 alkyl, and C 2-4 dihydroxyalkyl in which the carbon atom attached to the nitrogen atom does not carry a hydroxyl group and no carbon atom is substituted by two hydroxyl groups; R2, R 3, and R 4 are independently selected from C 1-4 alkyl, C 2-4 dihydroxyalkyl in which the carbon atom attached to the nitrogen atom does not carry a hydroxyl group and no carbon atom is substituted by two hydroxyl groups, or R 2 and R 3 together form a C 2-6 alkylene group which with the nitrogen atom to which R 2 and R 3 are attached forms a heterocyclic ring; X 1, X 2, and X 3 are independently selected from hydrogen, hydroxyl, NR 1 -A-NR 2 R 3 R 4 +(Z m-) 1/m, halogeno amino, C 1-4 alkoxy or C 2-8 alkanoyloxy; and (Z m-1) 1/m is an anion of charge m; or a derivative in which the group NR 1 is quatemarized together with A is a C 2-8 alkylene group; R 1 is selected from hydrogen, C 1-4 alkyl, and C 2-4 dihydroxyalkyl in which the carbon atom attached to the nitrogen atom does not carry a hydroxyl group and no carbon atom is substituted by two hydroxyl groups; R2, R 3, and R 4 are independently selected from C 1-4 alkyl, C 2-4 dihydroxyalkyl in which the carbon atom attached to the nitrogen atom does not carry a hydroxyl group and no carbon atom is substituted by two hydroxyl groups, or R 2 and R 3 together form a C 2-6 alkylene group which with the nitrogen atom to which R 2 and R 3 are attached forms a heterocyclic ring; X 1, X 2, and X 3 are independently selected from hydrogen, hydroxyl, NR 1 -A-NR 2 R 3 R 4 +(Z m-) 1/m, halogeno amino, C 1-4 alkoxy or C 2-8 alkanoyloxy; and (Z m-1) 1/m is an anion of charge m; or a derivative in which the group NR 1 is quatemarized together with at least a second fluorochrome or light-emitting compound, wherein the compound is of Formula or an N-oxide derivative thereof; wherein A is a C 2-8 alkylene group; R 1, R 2, and R 3 are independently selected from hydrogen, C 1-4 alkyl, C 2-4 dihydroxyalkyl in which the carbon atom attached to the nitrogen atom does not carry a hydroxyl group and no carbon atom is substituted by two hydroxyl groups, or R 2 and R 3 together form a C 2-6 alkylene group which with the nitrogen atom to which R 2 and R 3 are attached forms a heterocyclic ring; and X 1, X 2, and X 3 are independently selected from hydrogen, hydroxyl, NR 1 -A-NR 2 R 3, halogeno amino, C 1-4 alkoxy or C 2-8 alkanoyloxy. A is a C 2-8 alkylene group; R 1, R 2, and R 3 are independently selected from hydrogen, C 1-4 alkyl, C 2-4 dihydroxyalkyl in which the carbon atom attached to the nitrogen atom does not carry a hydroxyl group and no carbon atom is substituted by two hydroxyl groups, or R 2 and R 3 together form a C 2-6 alkylene group which with the nitrogen atom to which R 2 and R 3 are attached forms a heterocyclic ring; and X 1, X 2, and X 3 are independently selected from hydrogen, hydroxyl, NR 1 -A-NR 2 R 3, halogeno amino, C 1-4 alkoxy or C 2-8 alkanoyloxy.