In Vietnamese culture, the colour I'd pick is red. I'm a twenty-two-year-old university student in Da Nang studying tourism, and red is everywhere in my life, especially around Tet, our Lunar New Year.
People use it most during Tet and weddings. Before the New Year, families hang red decorations, put up red banners with lucky phrases and give children little red envelopes with money inside, which we call li xi. At weddings, the bride often wears a red ao dai for the traditional ceremony, and gifts are wrapped in red paper. Even shops paint their signs red when they open, because they hope it'll bring them customers.
Red represents luck, happiness and success. It's also believed to scare away bad spirits, which is why it's used at the start of something new, like a year, a marriage or a business. Interestingly, it's one of the colours of our national flag too, so it carries a sense of pride as well.
Personally, I have very warm feelings about it. When I see red lanterns going up in the streets in January, I immediately feel excited, because it means I'll soon go home to my grandparents' village. I associate the colour with family, food and noise, in a good way. That said, I've noticed foreign visitors sometimes find it a bit overwhelming, because in some cultures red means danger or anger. When I worked as a volunteer guide last summer, I enjoyed explaining that to tourists. I think understanding what a colour means in another country tells you a lot about what people there value.