"Pergelangan tangan saya biru."

Translation: My wrist is blue.

[Serfive]

Plural should be fine too, right?
I.e. ' my wrists are blue '

[win.metacutie]

man this word is long

[deactivated user]

I guess this is like in English when we say something is 'black and blue' meaning it's bruised/swollen after an accident or beating.

[Haakon388572]

Why isn't plural accepted here?

[Keith_APP]

Is there a meaning?

[Hans_Se]

Probably stained by a blue ink or bruises on your wrist ...