Why are colored inks used when printing grayscale?

[PeterBJ]

See this post and compare. It looks like the added dye inks make the black dots a deeper and more neutral black. The dots printed with pigment black only are a (very) dark brownish grey.

 

[Artur5]

Black inks never are neutral black. If you dilute a few drops of ink in a glass of water, you’l see different color hues. The compatible pigment black that I purchased for my Pixmas was greenish while photo black was purple. Other third party inks or OEM will have different color casts.