Dyes derived from dihydro-carbazolium salts

2-Methyl-4,4a-dihydro-3H-carbazolium salts that are useful as dye precursors and dyes derived from those precursors are disclosed. The salts are described by the formula wherein R1 represents an alkyl, aryl, sulfoalkyl, carboxyalkyl, sulfatoalkyl, alkoxyalkyl, acyloxyalkyl, dialkylaminoalkylene, cycloaminoalkylene, acyl, or alkenyl group having from 1 to 18 carbon atoms; R2 represents an alkyl group having up to 18 carbon atoms; R3 represents hydrogen or an alkyl group having from 1 to 18 carbon atoms; R4 represents hydrogen or an alkyl group having from 1 to 18 carbon atoms; R5 represents hydrogen, nitro, carboxyl, sulfo, hydroxy, halogen, phospho, or an alkoxy, thioalkoxy, oxyalkyl, acyl, alkyl, aryl, or amino group having up to 18 carbon atoms; wherein any two groups R5, or R4 and a group R5, or R1 and R4 may together form a substituted or unsubstituted aryl, heteroaryl, aliphatic, or heteroaliphatic ring; X represents an anion; and a and b represent positive integers such that a equals b. The salts have a partially saturated ring system that rigidifies the chromophore in the precursor and in dyes derived from it. The rigidified chromophores have narrowed absorption bands relative to corresponding non-rigid chromophores. Dyes prepared from the dye precursors of the invention typically have good solubility in non-polar solvents.