Although the vast majority of printer users refill their HP cartridges with dye based ink, it is sometimes necessary to use pigment instead. Many original HP printer cartridges use pigmented ink, and maintaining the status quo can be important in certain circumstances.
If you are intending to print onto transparencies or slicker surfaces, or if you want the image to last a long time, pigment ink is advised. Also if you are printing onto t-shirt transfer paper, pigment ink is more fade (UV) and water resistant than dye ink.
Premium Inks now offer a high quality set of pigment inks for HP printers which provide vibrant true to life colours. These are available from... https://premium-inks.com/collections/hp-refillable-cartridges-ink/products/4x100ml-pigment-printer-refill-ink-for-hp-inkjet-printers-non-oem