So, Color Kage are under the impression that...

[BlacLord™]

Because they colored it blue? dont about how accurate they are but if I remember correctly they also colored obito's chakra arms purple but in the official release it was colored yellow

Hence the title.

Or water in shapes of a needle, kinda like Tobirama's jutsu.
Senbons are needles, now it depends if they are made out of metal, water or whatnot [in NV ofc]

Senbon are specifically metal needles, for anything other, the word Hari is used.