A solvent-based ink composition for a thermal inkjet printhead comprises a surface-modified pigment. The ink composition comprises: (a) 10-80 wt. % of a compound of formula (A); [chemical expression included] wherein: R1 is C1-6 alkyl; and each of R2, R3 and R4 is independently selected from H, C1-6 alkyl, halogen, OH, and C1-6 alkoxy; (b) 10-80 wt. % of a C1-6 alcohol; and (c) 0.01-25 wt. % of the surface-modified pigment.