Concept is very abstract for many people. But it is an essential element for interior designer. Creative design is developed from a concept. After careful consideration of the actual environment, functions and customer's needs, together with creativity, a design concept is visualized.
Colors come from the materials used but easily affected by lightings. Lightings are essential because different lightings create different atmosphere.
A good design comprises many elements, space planning functions, materials, lightings, colors, furniture, ventilation system and a reasonable budget.