A colour circle is a visual chart that arranges the spectrum of hues in a circular format, illustrating the relationships between primary, secondary, and tertiary colours. Photographers and artists use the colour circle to understand colour harmony, contrast, and complementary combinations, helping to create visually balanced and appealing compositions. In photography, knowledge of the colour circle aids in lighting choices, post-processing adjustments, and creative colour grading, allowing photographers to enhance mood, atmosphere, and overall impact in their images.