In connection with ownership relations we normally add the ending -s to the noun (see 2.6 Nouns in the genitive).
| Kjolens farve er rød. | The colour of the dress is red. |
We may also use the preposition på.
| Farven på kjolen er rød. | The colour of the dress is red. |
Comparison:
Prepositions are used in the same way in English and Danish.