The purpose of the Environment Design (ED) for Main Control Room (MCR) of Nuclear Power Plant (NPP) is to provide and create an optimal working space to be free from physical, physiological and mental stress as well as environmental discomfort, based on the previous environment design experiences and to recommend the best ED including the color, the lighting and the interior design. Environment Design consists of three main areas: Human factor engineering design, Interior design with color design, and Lighting design. These design areas have been interactively cooperated in a way that each design specialist would share the objectives and concepts of the Environment Design for MCR. The specialists for Human Factors Engineering design had a corporative role in such a way to provide the guidelines for MCR design suitability of Interior and Lighting design considering the Human System Interface (HSI) safety concerns. This paper describes fruitful efforts to create the best fit for MCR ED among several design proposals with the design recommendations, impacts, and contributions to NPP environment.