Colour is a major element of fashion design, has a certain psychological effect on wearer and viewer. Fashion program students must be trained sufficiently and correctly for using colours in their designs. Within the author experience of teaching fashion designing at University of Nizwa, and with observing the importance and supremacy of black colour in outerwear Omani women Abaya, the author applied an experiment on fashion design program students, the objective of the experiment is to measure the effect of several fashion colour collections on the student’s psychology, guiding students to the psychological effect of colours, and for encouraging them to integrate several colours when designing black abaya, it’s a most challenging part for design a new fashion style for a conservative community. At the same time measuring and leading the students to designing originality, within designing by flat and 3D mixed colours ribbons on black velvet basic. The study followed the descriptive approach within designing and applying the study instrument, represented in opinion rating scale toward coloured fashion designs and the originality of proposed designs, the scale measured the psychological effect of (8), designs had been created by the author. The psychological effect behind fashion colours is classified into 2 thematic categories in current paper: a) the effect of rainbow colours fashion vs b) the effect of earthy colours fashion. The psychological effect behind fashion originality is classified into 2 thematic categories in current paper: a) the effect of decorating by flat ribbons vs b) the effect by decorating by 3D ribbons. The results indicated the tendency of the students toward rainbow colours collection with flat decorating ribbons. Results of current study may play a guiding role on colours effects studies and developing the aesthetics of producing new trend of Arabic black abaya in the future.