The primary color of the Australian flag is blue. The flag features a blue field, which provides a background for its central emblem and the Union Jack, symbolizing Australia's historical ties to the United Kingdom. The flag also includes the Southern Cross constellation, represented by five stars in white, which is a significant symbol of Australia’s identity and geography. The blue color in the flag represents the ocean and sky of Australia, reflecting the country's landscape and environment. Overall, the Australian flag combines elements that signify both the nation’s heritage and its unique characteristics as a sovereign country.