Marunouchi House Toilet is a renovation project of 65-square-meter restrooms located in Tokyo. I IN proposes an innovative use of colour to blur the boundaries between genders. By using yellow and green, adjacent colours at the center of rainbow spectrum – a symbol of gender diversity, the design softens the stereotypical gender division long associated with conventional codes of red and blue. The environment within the restrooms is saturated with coloured illumination respectively, bathing the users in light physically and mentally, to simulate a refreshing mind.