Questions & Answers about Veden väri on sininen.
Why is the word for water veden here instead of just adding an -n to vesi?
The basic word for water is vesi. In Finnish, many old words ending in -i change their stem before adding endings. The stem for vesi is vete-. When we add the genitive (possession) ending -n to say of the water, the t weakens to a d because of a rule called consonant gradation. So, vete- plus -n becomes veden.
Why is the order veden väri instead of matching the English order color of the water?
Finnish does not have a word for of. Instead, it uses the genitive case ending -n (which works exactly like the English apostrophe -s) to show possession or belonging. Just like in English you can say the water's color, Finnish puts the possessor (veden) right before the thing being possessed (väri).
Does the adjective sininen grammatically match the water or the color?
It matches the color. The main subject of the sentence is väri, which is in its basic dictionary form. Because adjectives must match the noun they describe, sininen is also in its basic form. If it were describing the water directly, it would have had to match the genitive form of veden.