Colour is usually the first design decision, but it should never be based only on personal taste. A bakery, jewellery showroom, hospital, hotel, school, cafe and electronics shop need different emotional tones. But all of them need contrast. Low-contrast colours make a sign look premium on a laptop screen and invisible on a busy road.
For safety and colour reference, the Bureau of Indian Standards and IS 9457 safety colours and safety signs are useful background sources. They show that colour has meaning, not only beauty. In brand signage, red can create urgency, gold can create premium value, blue can feel corporate, green can feel healthcare or organic, and black can create luxury when paired with bright lettering.