The present invention relates to a modified colorant comprising a colorant having attached at least one organic group. Various embodiments of the organic group are disclosed. For each of these embodiments, preferably the organic group has a defined calcium index value. Also disclosed are various uses for these modified colorants, including inkjet ink compositions.

The present invention relates to a modified colorant comprising a colorant having attached at least one organic group. Various embodiments of the organic group are disclosed. For each of these embodiments, preferably the organic group has a defined calcium index value. Also disclosed are various uses for these modified colorants, including inkjet ink compositions.

A composition includes a functionalized fluorescent dye. The functionalized fluorescent dye includes an isothiocyanate-containing dye that is functionalized with a functional group. The functional group includes a primary amine. The functionalized fluorescent dye can be mixed with a fluid to form a tracer fluid for tracing fluid flow in a subterranean formation.