When you talk about "national colours" of a country, you are basically referring to the colours that are associated with that country. In the case of the United Kingdom, the national colours are red, white, and blue.
These colours are important because they represent different things about the country and its history. For example, the red represents the monarchy and the blue represents the Scottish flag. The white represents peace and unity.
The UK's national flag is called the Union Jack, and it is made up of these three colours. The Union Jack is one of the most recognizable flags in the world and is usually associated with the UK.
Overall, the national colours of the United Kingdom are an important part of the country's identity and history. They represent different things about the country and are something that people from the UK are proud of.