Provided is a system to assist in designing of color distribution on an object surface while considering the relationship between characteristics of a particle group contained in the paint and the design effect or texture at the object surface achieved by the particle group. The system is configured to calculate and display color distribution in accordance with variation angle at the object surface so as to reflect the texture or design effect at the object surface achieved by the particle group based on the designated distribution mode of the particle group included in the coating layer at the object surface as well as designated shape characteristics and optical characteristics of the particles making up the particle group and based on color distribution in accordance with variation angle at the object surface stored.