The current article presents the importance of colours in day-by-day life of online marketing. With the accelerating progress in science as well as information and technology, marketing is always changing. The neuroscience of colour in relation to customer conviction is one of the numerous topics studied in marketing. As a starting point, the paper opens with a brief theoretical presentation of the consumer behaviour as the central element of marketing, while in the second part, a study of colours is clarifying the link between them and the perception of the customers. A good reason for everything that follows is represented by the fact that colour is pervasive and a source of knowledge. The paper presents the level of importance that colours represents in everyday online marketing. Marketing is permanently changing with rapid advances in science, information and technology.