"Our cat is white."
Translation:Nuestro gato es blanco.
I realize this is year late so you might not even care! But the answer is that possessive nouns, such as "nuestra/nuestro" do not describe the group of people who own the thing, but rather agree gender-wise with the thing that is owned. So even if it was a group of women that owned a male cat, you would still use "nuestro". If a group of men owned a female cat, it would be "neustra" to agree with the female cat, "gata"